Sponge cakes
2 egg whites
10 ounces almond paste
12 large eggs, separated
1 1/3 cups/10 ounces granulated sugar
1 teaspoon vanilla extract
2 3/4 cups/8 ounces cake flour, sifted
2/3 cup/1 ounce natural (not Dutch process) cocoa powder
Buttercreams
1 pound unsalted butter, softened
5 ounces margarine, softened (don't substitute butter)
1 cup egg whites (from 7 or 8 eggs)
1 pound sugar
1 teaspoon vanilla extract
6 ounces melted dark chocolate
1/2 cup brewed espresso (not instant), cooled
For Assembly
1/4 cup brewed espresso, cooled
1/3 cup water
1/2 cup toasted sliced almonds
Dark chocolate shavings
Other
2 10" cake pans
Parchment paper rounds
Cardboard cake rounds
Prepare the spongecakes:
Mash the almond paste with the back of a spoon to break it apart and get out the lumps (see note above). Mix in the two egg whites and set aside.
Preheat oven to 375 degrees. Line two 10" cake pans with parchment rounds and set aside.
Place the egg yolks in a mixing bowl on stand mixer and add 1/2 cup of the sugar. Beat with the paddle attachment on medium-high speed until the egg yolks are pale yellow and the mixture falls in a ribbon if the beater is lifted, at least 5 and preferably 10 minutes. Add the vanilla.
Gently stir the yolks into the almond paste with a spatula and set aside.
In another mixing bowl, whip the egg whites on medium-high with the whisk attachment until they foam, then slowly add the rest of the sugar. Beat just until the egg whites form stiff peaks. Carefully fold the egg whites into the almond paste mixture. Gently fold in the flour with a spatula, being careful not to deflate the egg whites. Pour a little less than half of the mixture in one of the prepared cake pans, smooth the top and set aside.
Sift the cocoa powder into the remaining batter and fold in to combine - don't overmix! Put the remaining batter in the second cake pan and smooth the top. Place both layers in the preheated oven and bake 23-25 minutes, until tops spring bake when touched. Remove layers from oven and cool completely on a rack.
When cool, run a thin, sharp knife around the edge of each cake layer and invert onto a rack. Peel off parchment paper and invert again (so top of layer is up).
Prepare the buttercream:
Beat together the the butter and margarine in a small bowl and set aside.
Combine the egg whites and sugar in a mixing bowl and place the bowl over a pan of simmering water and whisk constantly for about 3 minutes or until the sugar is dissolved. Be careful not to cook the egg whites!
Remove the bowl from the pan and place it on a stand mixer fitter with the whisk attachment and whip until the mixture has cooled considerably and has formed stiff peaks. Lower the speed of the mixer and add the vanilla extract. With the mixer still on low, gradually add the butter mixture and whip until combined.
Divide the buttercream (you'll have about 6 cups total) into two bowls. Add the melted chocolate to one bowl and stir with a spatula to combine, and add the 1/2 cup expresso to the other bowl, similarly using a spatula to combine. Set both bowls aside.
To assemble the cake (the fun part):
Cut the almond sponge into three even layers. Reserve the top layer for another use (you'll only need two almond layers). Cut the chocolate sponge into three even layers.
Combine the 1/4 cup espresso and water in a small bowl. Place one of the chocolate layers, cut side up, on a cardboard cake round. Using a pastry brush, lightly moisten the layer with the expresso mixture. Spread a layer of mocha-flavored buttercream and shave it down to about 1/4" thick, bringing it to the edge of the layer.
Place an almond layer on top of the mocha buttercream. Moisten the almond layer with the espresso mixture, then spread a layer of the mocha buttercream and shave it down to about 1/4" thick, bringing it to the edge of the layer.
Repeat with another chocolate layer, brushing the chocolate layer with the espresso mixture and adding the buttercream and then ending with an almond layer on top. Don't brush the almond layer or top it with buttercream. You will have one chocolate layer left. Chill the cake for 15 minutes to set the buttercream.
To cut the cake, dip a sharp, thin knife (I find a boning knife works better than the serrated knife that the recipe calls for) in hot water and wipe dry. Holding the knife at approximately a 30 degree angle approximately 3/4" in from the edge of the cake, carefully and gently cut a cone-shaped section from the center of the cake, about 8" wide at the top and and 2" wide at the bottom (or "tip"). Think of it as the crater of a volcano. Wipe your knife clean. Place your hand flat on the top of the cone-shaped wedge and using the knife or an icing spatula, remove the wedge and invert it onto your hand. Place the cone-shaped wedge, flat side down, on a cardboard cake round or a plate lined with parchment paper and set it aside.
Working inside the "crater," spread a layer of chocolate buttercream, about 1/4" thick, lining the inside of the crater.
Place the reserved chocolate sponge layer on top of the cake (almost like putting a roof on top of the crater). Place a cardboard cake round on top and invert the cake so the new chocolate layer is now on the bottom and the first almond layer is on the top. Cover the cake and set it aside (not in the refrigerator) to let the buttercream soften in between the layers.
Now, reconstruct the crater. To do this, gently press on the center of the top of the cake, gently pushing the inverted crater down to meet the bottom layer. In this new crater, spread a layer of chocolate buttercream all the way around and to the edge, making sure the buttercream is about 1/4" thick. The crater won't seem as deep or as sharp around the edges, and that's OK.
Invert the cone-shaped wedge and set it, pointy side down, flat side up, in the crater, and gently press it into place (if needed). Using a chef's knife, trim the sides of the cake to the original shape (in the event reconstructing the cake has made bits stick out, you can trim it a little to make it round again).
Spread the remaining chocolate buttercream on the top and sides of the cake. Press the toasted almonds around the side of the cake. Top the cake with dark chocolate shavings if desired.
Serve immediately, or refrigerate until needed. Set out at room temperature 20-30 minutes before serving.
Recipe adapted from Cooking at the Academy by way of Lethally Delicious blog