Brooklyn Blackout Cake – Gluten-free, Dairy-free

Ollie

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The idea of the Brooklyn Blackout Cake came about during WWII, when blackouts were carried out, so that ships sailing off to battle from the Brooklyn Naval Yard could not be silhouetted and potentially spotted by enemy aircraft. It was one of the drills performed by the Civilian Defence Corps: city lights were turned off and all windows were covered with black material. It is for this latter practice that the cake is named. The cake was made popular by Ebinger’s Bakery (1898 - 1972), that had stores in Brooklyn, New York. Originally, a multi-layered butter cake topped with chocolate icing, it was later changed to a chocolate on chocolate (black on black) cake. The cake is no longer commercially made.
Basically, the Brooklyn Blackout cake is a chocolate pudding cake, with a chocolate icing that is covered with chocolate cake crumbs (the cake is ‘blacked out’). The components of the cake are made up of: alternative layers of chocolate sponge cake covered with chocolate pudding, which were then topped with a final layer of chocolate sponge cake, which itself was topped with a dark chocolate icing that covered the sides too. Finally, the whole cake was covered with chocolate cake crumbs. Basically, it is a chocolate delight: in fact, it is a chocolate indulgence.
This gluten-free version is based upon the gluten recipe posted by Shirl Gard (.com) in 2017. It is made using: Devil’s Food sheet cake; Old-fashioned chocolate pudding; and Bittersweet chocolate ganache. Devil’s Food sheet cake is made like an old-fashioned mayonnaise cake, such as was popular during WWII. The mayonnaise acts as an emulsifying oil, allowing the chocolate sheet cake to be moist, rich and tender, and at the same time avoiding the taste of oiliness that sometimes happens through the use of too much butter. The Old-fashioned chocolate pudding is adapted by Shirl Gard from the original recipe given in Larry Forgione’s book An American Place Cookbook, (1996, William Morrow & Co., New York), adapted to make it more chocolaty, although it does not contain as much chocolate as some French pot de crème recipes. It offers just the right balance with the chocolate sheet cake and chocolate icing. The Dark chocolate ganache is based upon that adapted by Shirl Gard for a Bittersweet chocolate ganache, which came from the recipe she obtained from Eric Perez of the French Pastry School in Chicago: adapted to make it more user-friendly for home bakers. It can be used as a glaze, filling or as an icing. It is a less rich version of a regular ganache, as half of the normal cream amount is replaced by sugar syrup, and it is softer than regular ganache too. Dairy-free is an option; by using Hemp milk instead of cow’s milk to make the Old-fashioned chocolate pudding, and using Hemp milk for making the Heavy cream in the Dark chocolate ganache.
Making the cake is easily achievable by the home baker; it just takes time. Yet, it is well worth the effort. The cake itself is built up within a cake ring, and involves freezing overnight before cutting and glazing. Hence, making the Brooklyn Blackout cake is split over three or more days. The first: to make the sheet cake rounds; to make the old-fashioned chocolate pudding; and the Dark chocolate ganache. On the second day: to assemble the cake rounds and fillings. And finally, on the third day to: to ice, coat, and decorate the cake. Working this way takes the stress out of making the cake. Patience is the key, as is the chilling process used throughout; to yield the right textures.
The cake uses Heavy cream, which is considered a stock item, and, if using the Hemp milk alternative, this will need to be made in advance.
The recipe makes one 20cm (8 in) cake, and it serves 8 - 12 people, depending on appetites - it very rich.
Components:
Devil’s Food Sheet Cake
Old-fashioned chocolate pudding filling
Bittersweet chocolate ganache (used for both “dam” filling, icing and piping decoration)

Day 0
If not making the substitute Heavy cream, skip to the section entitled: Day 1, Devil’s Food Sheet Cake.

Hemp milk Heavy cream

Ingredients:
(makes approximately 600g)
Butter (sliced) 238g
Hemp milk 360g plus 2Tbsp
Gluten-free flour mix* 16g (to thicken the liquid)
Cane sugar 8g
*Gluten-free flour mix: 440g Brown Rice flour, 125g Sweet Rice flour, 45g Potato starch, 95g Tapioca starch, and 55g Arrowroot. Total weight: 760g

Method:
Place 238g sliced butter in the top bowl (1) of a double boiler, gently heat until three quarters of the butter is melted, stirring with a spoon. Remove from heat and melt the rest of the butter with a spoon. Set aside the bowl to cool.
In a saucepan (2), warm the Hemp milk just to finger warmth (36 - 37C) and then remove from the heat.
Pour half of the warmed Hemp milk into the cooling melted butter and combine with a hand whisk.
Pour the butter-milk mix back into the warmed Hemp milk and combine with a whisk.
In a small bowl (3), mix 16g Gluten-free flour mix* with 2Tbsp Hemp milk and combine with a small whisk, and then pour the mix into the milk-butter mix, and combine to thicken.
Transfer the thickened milk-butter mix into a tall storage jar. Blend with a hand, or stick, blender for 5 minutes. This is to disperse the butterfat globules into the Hemp milk liquid to produce the Hemp milk Heavy cream.
Place a lid on the storage jar and store in a refrigerator for 20 – 30 minutes before use. It will keep for several days in the fridge. It is best left in the refrigerator for a minimum of 12 hours before whipping.

Day 1
The first thing to make on Day 1 is the Devil’s Food Sheet Cake, which, after baking, is placed in a freezer to chill for cutting. This is followed by making the old-fashioned chocolate pudding and storing in a refrigerator. Finally, making the Dark chocolate ganache, and storing that too.

Devil’s Food Sheet Cake
The ingredients below are for one half sheet pan only, two will be needed (to make three cake rounds), so, either double the ingredients, or just make it twice.

Ingredients:
Gluten-free flour mix* 200g
Cocoa powder (alkalised) 60g (Dutch processed)
Baking soda/Bicarbonate of soda 1tsp
Sea Salt 1/4tsp
Gum Arabic 1tsp (or 1 1/2tsp Guar gum)
Eggs (room temperature) 110g (2 large) plus 10g egg yolk
Cane sugar 250g
Vanilla essence 3/4tsp
Mayonnaise 170g
Water (room temperature) 210g
Instant coffee 1 1/2tsp
Melted dark chocolate (72%) 120g (for glazing the bottom of the cake)

*Gluten-free flour mix: Brown rice flour 440g; Sweet rice flour 125g; Potato starch 45g; Tapioca starch 95g; Arrowroot powder 55g. Total weight: 760g

Method:
Line a half sheet pan, or baking tray (33 x 45cm (13in x 18in)) with parchment paper and lightly grease.
Place an oven rack in the middle of the oven and preheat the oven to 165C (for this recipe, a convection oven, that heats fairly accurately, was used at this temperature) for 45 minutes.
Sift Gluten-free flour mix and bicarbonate of soda in a bowl (1), add the instant coffee, cocoa powder, Gum Arabic, and salt, and then whisk to combine.
Place the eggs and egg yolk, lightly combined, in the bowl of a stand mixer (2) (or the bowl of a hand mixer) fitted with a whisk attachment and mix at low speed for about 1 minute to combine.
Gradually dribble in the cane sugar as the mixer is running, stopping and scraping down the sides and bottom of the bowl as required. Turn the speed up to high and continue to whip until the mixture is thick and pale in colour. This will take approximately 10 minutes. At the end, when the whisk is lifted the mixture should form a slowly dissolving ribbon.
Turn the speed down to low, add the vanilla essence and combine. Then add the mayonnaise, a spoonful at a time, and combine.
Remove the mixing bowl (2) and fold in one third of the Gluten-free flour mix with a large rubber/silicon spatula; add half of the water and combine, ensuring that all of the flour is incorporated. Repeat with another third of the Gluten-free flour mix and the other half of the water. Finally, fold in the remaining third of the Gluten-free flour mix until it is fully combined (making sure to reach all the way down to the bottom of the bowl (where the flour likes to settle)). The batter will be very thin.
Pour the batter into the prepared half sheet pan and spread the batter with an offset spatula held at a slight angle, spread the cake batter evenly over the tray with a rapid back and forth movement (‘wax-on, wax-off’) in a motion that is quick and light, making sure that the batter reaches right into the corners. Use a rubber/silicon spatula to scrape off any batter that adheres to the offset spatula.
Place the filled pan in the preheated oven and bake at 165C for approximately 25 minutes, or until a paring knife inserted into the middle of the sheet cake comes out clean, and the sheet cake is starting to pull away from the sheet pan sides, and the cake springs back when lightly touched.
Let the Devil’s Food Sheet Cake cool in the pan completely.
Place a silmat, or a sheet of parchment paper, on top of the cooled cake and carefully flip over on to the worksurface. Remove greased parchment paper on the bottom of the cake.
Cover the Devil’s Food Sheet Cake with two layers of overlapping clingfilm. Place the cake back in the sheet pan; place it in the freezer for at least 1 hour, or preferably, overnight, as freezing makes it easier to cut.
Wrapped completely in at least two layers of clingfilm, the cake can be left at room temperature for up to four hours; for up to 3 days in a refrigerator, and up to 2 weeks in a freezer.

Old-fashioned chocolate pudding
This is for the filling; it makes enough for two layers of approximately 200g each.

Ingredients:
Hemp milk 285g (250g + 30g)
Cane sugar 50g (25g + 25g)
Eggs 50g (1 Large)
Egg yolks 16g (1 Large)
Cornstarch 10g
Cocoa powder 8g
Fine sea salt pinch
Dark chocolate 70g
Butter 15g
Dark rum 1tsp
Vanilla essence 1tsp

Method:
Take 15g butter out of the refrigerator, at least 30 minutes before use, and bring it up to room temperature.
In a bowl (1) add 10g Cornstarch, 25g Cane sugar, 8g cocoa powder, and pinch fine sea salt, and mix to blend. In a medium sized bowl (2) add 30ml Hemp milk, egg and yolk and whisk together until blended. Add the blended dry ingredients (bowl 1) to the milk-egg mixture (bowl 2), and whisk together for a minimum of 30 seconds (otherwise the egg yolks will burn due to the acid in the sugar), to form a smooth.
In a saucepan (3) add 250ml Hemp milk, 25g Cane sugar, and stir together with a wooden spoon. Place over medium heat and bring to a fast simmer, just under boiling.
Turn off heat. Slowly pour half of the hot milk mixture (3) into the egg mixture (2) and stir constantly with a wire whisk. This is called tempering, and is a method of easing two components with widely different temperatures to cook together and prevent premature coagulation: to control the rate of protein folding and reconnecting.
Pour the resultant mixture (2) back into the saucepan containing the remaining milk mixture (1) and whisk together to combine.
Turn heat back on to medium-low, for even unfolding and reconnection of the egg proteins, and stir the pastry cream mixture with a wooden spoon until it is thoroughly blended and smooth. Make sure that wooden spoon reaches everywhere - bottom, sides, and corners, so that the mixture does not burn. Keep the wooden spoon in constant motion. Once you sense that the mixture is slightly thick on the bottom of the saucepan (look at bottom of spoon), remove it from the heat. Once the mixture has reached 75 – 77C the egg proteins reattach and solidify. Heating above 77C will result in an ‘eggy’ taste to the custard.
Off heat, continue stirring the pastry cream mixture for a further minute, until the mixture is thick, smooth and uniform (this allows a slow and even coagulation of the eggs and will produce a creamy texture).
Return the saucepan to the heat and bring the pastry cream mixture to the boil (to fully incorporate the cornstarch) whilst stirring constantly (this will inactivate the yolk amylase enzyme and will extract starch, and the egg proteins will bond strongly). Cook for a further 1 – 2 mins to overcome any resultant starch flavour.
Remove from the heat, add the chopped chocolate, butter, rum, and vanilla essence; jiggle the saucepan to immerse the chocolate. Stir with a wooden spoon until the chocolate and butter have completely melted (at least two minutes).
Strain and pour the pastry cream into a cold flat-bottomed bowl (4) (otherwise the pastry cream will continue to cook) and place into a larger bowl (5). Fill bowl (5) with ice cold water to the height where pastry cream bowl (4) just begins to float. Initially continue stirring, then stir only occasionally and minimally as the pastry cream cools (as stirring breaks developing starch networks, which results in a thinner pastry cream).
Alternatively (preferred method), line a baking tray with clingfilm, and pour the pastry cream into this, ensuring that it is thinner than 5cm (2in) in thickness, and cool to room temperature. It is cool when the bottom of the baking tray feels cold. Using a rubber, or silicon spatula roll up the Old-fashioned chocolate pudding to one end of the baking tray and scoop into a bowl. Tightly cover the surface with clingfilm and place in a refrigerator overnight.
The Old-fashioned chocolate pudding should be thick, creamy, and smooth, indicating that the fat, in the butter, milk, and eggs, has been properly emulsified with the water in the milk and eggs. The pudding will thicken as it cools.

Dark chocolate ganache
This for both the ‘dam’ and the icing (and piping if desired).

Ingredients: (makes approximately 1500g)
Dark chocolate (72%min) 750g
Water 125g
Cane sugar 155g
Glucose/Light corn syrup 155g
Hemp milk Heavy Cream 440g

Method:
Chop dark chocolate and set aside (bowl 1)
In a saucepan (2), add water, sugar and glucose; place the saucepan over medium heat, add the Hemp milk heavy cream, and bring to a boil (the liquid will rise up the sides of the saucepan).
Take the sugar-cream mix (saucepan 2) off the heat, and add the chopped dark chocolate (bowl 1); shake the saucepan to settle the chocolate, and let it rest for 1 minute.
Using a wooden spoon, or a silicon spatula, stir the mixture, gently, starting in the centre of the saucepan, and using a circular motion, work out to the sides. Stir until all of the chocolate is melted (approximately 2 minutes (min)) and is fully emulsified.
Using an immersion blender, mix until the Dark chocolate ganache is shiny and smooth.
Strain the ganache through a fine mesh sieve (to remove any air bubbles) into a bowl (3).
Line a baking tray with clingfilm, and pour the ganache into this, ensuring that it is thinner than 5cm (2in) in thickness. It is cool when the bottom of the baking tray feels cold. Using a rubber, or silicon spatula roll up the ganache to one end of the baking tray and scoop into a bowl. Tightly cover the surface with clingfilm and place in a refrigerator overnight.
The dark chocolate ganache can be stored, tightly covered, in a refrigerator for up to two weeks.

Day 2
Day 2 is concerned with: cutting the cake rounds; making fine cake crumbs from the Devil’s Food sheet cake left overs; and the first part of assembly of the cake components.

Cutting the cake rounds
Remove the Devil’s Food Sheet Cake from the freezer, and unwrap from the clingfilm.
With a paring knife, cut two 20cm (8 in) cake rounds from the sheet cake, using a 20cm (8in) cake board as a guide. Three rounds in total are required. Stack the cake rounds with a layer of parchment paper in between each round. Optionally, coat, or paint, the bottom surface of one cake round (the base layer) with a layer of melted chocolate (approx. 120g), and let it cool.
The trimmings left over will be used to make fine cake crumbs.

Making fine cake crumbs
Cut the trimmings into cubes of cake. Spread the cubes on a half sheet pan; place it in the middle shelf of an oven, turn the heat up to 80C, and dry the cake cubes for one hour. Remove the dried cake cubes from the oven, and allow them to cool completely; then, in a food processor cut them into crumbs, or use a coffee grinder to make finer crumbs. Set aside, or store in a container in a freezer.

Assembly 1
The cake is assembled using a cake pan, springform pan, or entremet ring, which is first of all lined.
The first task is to prepare the cake pan used for the assembly of the cake. If the selected cake pan (20cm (8in) diameter by approximately 6cm (2 3/8in) deep) does not have a removeable bottom, line the pan with overlapping layers of clingfilm that extend above the pan sides (so that it will be easy to lift the assembled cake out of the pan). For cake pans with removeable bottoms, adjustable entremets rings, or springform pans this is not necessary. Next, place a 20cm (8in) cake board in the bottom of the cake pan. Then, either, use a 8cm (3 1/8in) strip of parchment paper, approximately 66cm (26in) long, or a similar sized strip of acetate cake band, and line the side of the cake pan. It is alright if the cake band or strip of parchment paper overlap.
Place one cake round centrally in the bottom of the cake pan, or ring, with the chocolate coated side downwards (if that option is taken).
Fit a 13mm (1/2in) plain piping nozzle into a clean piping bag.
Take the Dark chocolate ganache out of the refrigerator, place the bowl over a saucepan containing a small quantity of simmering water, and whilst gently chopping up and stirring the Dark chocolate ganache, heat it up to melt and then cool to 21C. Immediately fill the prepared piping bag with the warmed Dark chocolate ganache. Note that this ganache will cool very quickly if the ambient temperature is below 21C, as may be the case in winter. So, in order to get it to pipe it may be necessary to stop the cooling above 21C, in order to load the piping cone, and get it to pipe at 21C, without stiffening up too much.
Pipe a “dam” (that is to hold in, contain, the Old-fashioned chocolate pudding within) of Dark chocolate ganache in a circle around the top, outside edge of the cake round. When complete, place the piping bag in a place where it will not cause a mess (a storage jar perhaps), or if there is insufficient filling to pipe a second “dam”, pipe the ganache back into the vessel containing the ganache.
Take the Old-fashioned chocolate pudding out of the refrigerator, weigh out 200g, and spoon it onto, and spread it over, the top of the cake round, to fill in the space created by the Dark chocolate ganache “dam”.
Centre, and place a second cake round over the top of the filling and “dam”, and repeat the above process of piping a “dam” and filling with Old-fashioned chocolate pudding. Then, place the third cake round on top, as before. Wrap tightly with clingfilm, and place the wrapped, filled cake pan in a freezer overnight.

Day 3
Assembly 2

The final assembly is concerned with finishing the cake for serving: removing the cake from the cake pan; coating the top and sides of the cakes with Dark chocolate ganache; coating the sides of the cake with Devil’s Food chocolate cake crumbs; and, finally, decorating the cake as desired.
Take the cake out of the freezer, and place on a work surface. Unwrap the clingfilm from the cake pans (of whatever type). Lift the cake out of the cake pans with the overhanging clingfilm, and then remove the clingfilm from the cake completely. Remove either parchment paper or acetate rings from the cake sides. Keep the cake board under the cake in place.

Dark chocolate ganache icing
Remove the Dark chocolate ganache from the refrigerator, check the temperature, stir it with a silicon spatula to soften it, and allow it to come up to 23C, melting it in a bowl over a saucepan containing a small amount of simmering water, and then cooling. Remember that in winter it will cool very quickly if the ambient temperature is below 22C
Centrally, place a small amount (‘dob’) of the ganache (to anchor the cake whilst icing) on top of a cake turntable, or ‘lazy Susan’, or similar; cover with four wide strips of parchment paper to form a rectangle of strips that extend outside of the cake (this is to catch excess ganache icing, smears, etc.); and place the cake on top.
Using a metal icing spatula, place a large amount (“dollop”) of Dark chocolate ganache on the top surface of the cake. Using a back-and-forth motion spread the ganache evenly over the top surface, and ensure that ganache extends over the cake edges.
Scoop up a dollop of ganache on a straight metal icing spatula and apply the ganache to the side of the cake; then using a paddle motion, spread the ganache circumferentially. Repeat this process around the whole cake. Layer on more ganache to cover any gaps.
Hold a bench scraper, fixed, in one hand, press it against the ganache (to avoid air pockets) whilst simultaneously turning the cake with the other hand. This action will smooth the side of the cake.
To level the top of the cake, take a long straight edge, hold it level with both hands, such that the top level of the straight edge is at an acute angle to the ganache surface and facing towards to the other side. Confidently, sweep the straight edge forward whilst gradually rotating it so as to finish with the blade at an obtuse angle to the ganache surface (top edge of the blade pointing back to the start) at the far side of the cake, and with excess ganache sitting on the blade surface. Place the excess ganache back in the bowl. If there are any gaps, or dips, add more ganache and repeat the levelling process.
There will be excess ganache hanging over the side of the cake. Use the bench scraper to smooth the side of the cake again, thus taking off most of the excess, which is returned to the bowl. Now there is excess ganache sticking up around the circumference of the cake. Take this off with a small metal spatula. Repeat the side and top levelling until all of the excess ganache is removed. Finally, smooth the top with an offset metal spatula warmed in hot water, and smooth the side with a bench scraper similarly warmed in hot water.
Store the excess Dark chocolate ganache in a refrigerator, with the top surface of the ganache tightly covered with clingfilm, for up to two weeks.
Carefully remove the four parchment paper strips with the help of a thin metal spatula to lift up the cake.

Coating the cake sides with chocolate cake crumbs
Pour the cake crumbs into a large bowl; scoop out a handful of cake crumbs and pat the them over the sides of the cake. If the ganache becomes too hard, and the cake crumbs do not stick; warm a tea cloth in a microwave oven, and then place it on the cake side, a small area at a time, to soften the ganache, or use a hot icing spatula; then continue to apply the cake crumbs. When complete, use a pastry brush to sweep up the excess cake crumbs that are lying on the turntable, and place them back into the container. Some baking authors coat the top surface with cake crumbs too. (both options are shown in the photographs)

Decorating/piping
Fit a 13mm (1/2in) fluted piping nozzle into a clean piping bag.
Remove the Dark chocolate ganache from the refrigerator, and warm, as before, to 21C. Immediately fill the prepared piping bag with the warmed Dark chocolate ganache. Pipe eight swirls of Dark chocolate equally spaced around perimeter of the cake top. Or decorate as desired.

Serving
Place the finished Brooklyn Blackout cake on a platter or cake stand, and allow the cake to fully come to room temperature. Cut the cake in half, separate one side, slightly, and then cut segments from it.

Storing
The cake will keep at room temperature for 2 to 3 days in a cool place. However, it is best if it is covered and stored in a refrigerator.

Enjoy!!!
Note: the photographs show the cakes covered with the finer cake crumbs.

Cake with full coverage of cake crumbs
Brklnblkoutcake 1.jpg
Brklnblkoutcake slice.jpg

Side only coverage by cake crumbs
Brklnblkoutcake 2.jpg
 

Tuulikki

Jedi Master
I wish I hadn't read this straight after my breakfast. Quite a healthy one too. I am now craving chocolate and heading into the kitchen shortly to sort out a coffee and something chocolately - not the above cake sadly - but something tasty. This sounds gorgeous BTW. Oh what it is to be a weak willed soul in the food department.🎂 :nuts:
 

Tuatha de Danaan

The Living Force
FOTCM Member
My word that looks scrumptious. However, with the best will in the world, three days would allow me to prepare a banquet. Those ingredients would not last past the testing and tasting stage.

However, like Gandalf, I would love to order one a month.

Who knows, maybe as this lockdown continues it would certainly keep a family who have children quite busy for a few days. Thanks for the suggestion. I'm off for a cigarette now instead of raiding the biscuit barrel.
 

beetlemaniac

The Living Force
That cake looks amazing! I've been swearing myself of chocolate these days but I don't know if I might be a little too strict in that department. Thanks for sharing Ollie :-)
 
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