Chocolate Opera Cake

Instructions

Make the chocolate cake

1. Preheat oven to 325 degrees. Line a 13x18-inch rimmed baking sheet with parchment paper or a silicone baking mat. Grease with butter or nonstick baking spray (NOT cooking spray).
2. In a small mixing bowl, whisk together the cocoa powder, flour and salt. Set aside.
3. Bring about an inch of water to a boil in a saucepan. In a large mixing bowl, beat together the eggs and sugar with a hand mixer.
4. Once the water in the saucepan comes to a boil, reduce the heat to simmer the wate. Set the mixing bowl over the water, continuously beating the egg mixture with the hand mixer until it lightens in color and doubled in volume.
5. Remove the mixing bowl from the double boiler (do not discard the simmering water, you'll need it again later). Continue beating the egg mixture another three minutes or so, until it is very thick and sits on top of the rest of the mixture for 5 to 10 seconds when a spoonful is dropped into the bowl.
6. Sprinkle the dry ingredients over the egg mixture, and use a spatula to gently but quickly fold them together, then fold in the melted butter.
7. Scrape the cake batter into the prepared pan, and use an offset spatula to gently spread the cake batter to cover the whole pan.
8. Bake for 5 to 6 minutes, until springy to the touch. Remove from the oven to a wire rack to cool.

Make the coffee syrup

1. Combine the water, sugar and espresso powder in a small saucepan. Bring just to a boil over medium-high heat.
2. As soon as the mixture boils, turn the heat off and let the mixture cool to room temperature.

Make the coffee buttercream

1. Bring the water in the bottom pan of the double boiler back up to boiling.
2. In the bowl of a stand mixer, combine the egg whites and sugar. Whisk over the boiling water until the sugar dissolves.
3. Place the bowl on the stand mixer and, using the whisk attachment, beat the mixture on medium-high speed until medium peaks form. If by then the whites are still hot, lower the speed to medium-low, and continue whisking until the bottom of the mixing bowl is just warm to the touch.
4. While the meringue is cooling, combine the Kahlua and espresso powder in a small bowl. Stir until the powder dissolves.
5. Once the meringue has cooled down, switch to the paddle attachment, and begin adding the softened butter, 1 to 2 tablespoons as a time, mixing on medium speed between each addition.
6. Once all the butter is added, turn the speed up to medium-high and beat until the icing is fluffy. Lower the speed to medium low and drizzle in the Kahula/espresso mixture, then return the speed to medium-high until the buttercream is uniform.
7. Transfer to another container, and clean out the bowl and the whisk attachment for making the ganache.

Make the ganache

1. Place the chopped chocolate in the bowl of a stand mixer.
2. Place the cream in a small saucepan. Set the heat to medium, and bring just to scalding. Keep a very close eye on it -- with this small amount, it won't take very long.
3. Pour the hot cream over the chopped chocolate and let stand for 1 minute, then whisk until smooth. Measure out about a third of the ganache to a separate container that can be warmed over a double boiler or in the microwave. Set the remainder aside to cool.
4. Once the larger portion of the ganache has cooled, whip it with the whisk attachment of the stand mixer until it forms a thick and fluffy icing.

Assemble the Opera Cake

1. Lay a sheet of parchment on a cutting board. Use a knife to release the chocolate cake from the edges of the jelly roll pan. Flip the cake onto the parchment paper, and peel away the parchment or silicone paper that the cake was baked on.
2. Arrange the cake so that one long edge is facing you. Use a sharp chef's knife to cut the cake into three rectangles about 4 inches by 9 inches each.
3. Place one of the thirds on a rectangular cake board. Brush with about third of the coffee syrup.
4. Spread about half of the coffee buttercream over the cake in an even layer.
5. Top with another third of chocolate cake. Brush with another third of the coffee syrup.
6. Spread the beaten chocolate ganache over the cake in an even layer.
7. Top with the remaining third of the chocolate cake. Brush with the remaining coffee syrup.
8. Spread the remaining half of the coffee buttercream over the top in an even layer, getting the top as smooth as possible.
9. Chill the cake, uncovered, in the refrigerator for 15 to 30 minutes.
10. While the cake is chilling, gently re-warm the reserved ganache, either over a double boiler or in the microwave for 30-second bursts, stirring in between each burst, until it reaches a pourable consistency.
11. Remove the opera cake from the refrigerator and gently smooth the top of the icing with a non-patterened paper towel (Viva paper towels are great for this).
12. Have a large offset spatula at the ready, and pour the chocolate ganache over the opera cake. Use the spatula to swipe the ganache smooth and nudge it to the sides and corners of the cake. There isn't much time to do this before the chilled cake starts to set the ganache, so work quickly.
13. Place the cake back in the refrigerator another 30 minutes to chill the ganache.
14. Trim the cake: run a very sharp chef's knife under hot water, wipe it dry, and cut off one edge of the opera cake. Rinse the knife under hot water, wipe it dry, and repeat with another edge. Repeat until all four edges are trimmed.
15. If you like, you can scrape any remaining ganache from the bowl into a piping bag and write the word "Opera" on the top of the cake. Chill the cake again until the ganache is set, then cover in plastic wrap and store the cake in the refrigerator for up to 3 days.