Classic French Opera Cake

Note: while there are multiple steps to this recipe, this dessert is broken down into workable categories to help you better plan for baking.

Make the Almond Sponge Cake

1. Gather the ingredients.

2. Position two racks in the upper and lower third of the oven and heat to 425 F. Line two 15-inch by 12-inch rimmed pans with parchment paper and brush the surface of the paper with butter. Set aside.

3. In the bowl of a stand mixer with the whisk attachment, or an electric beater on high speed, beat the egg whites until they become foamy and start to expand. Sprinkle in the sugar, one teaspoon at a time, beating between additions, until all of it is incorporated into the egg whites. Continue beating the meringue until it is glossy and holds stiff peaks.

4. In a separate large bowl, beat the ground almonds, confectioners' sugar, and whole eggs on medium until the mixture becomes light and foamy.

5. Gently stir the all-purpose flour into the almond batter.

6. Gently stir 1/4 of the almond batter into the whipped egg whites. Fold the remainder of the almond batter and the 3 tablespoons melted, cooled butter into the egg whites.

7. Divide the sponge cake batter between the two prepared pans and bake the cakes until the surfaces spring back from a light touch, 5 to 7 minutes.

8. Cool the cakes slightly. Cover the top surface of each cake with a fresh piece of parchment and carefully invert them onto a clean surface. Slowly peel back the old parchment and allow the paper to rest loosely over the cakes to prevent them from drying out.

Make the Coffee Buttercream

1. Gather the ingredients.

2. Stir the espresso powder and boiling water together until the powder dissolves. Set aside.

3. In a medium saucepan over medium heat, bring the sugar, water, and vanilla to a boil. Continue cooking it until it reaches 255 F on a candy thermometer. Remove the sugar syrup from the heat and allow it to cool slightly.

4. In the bowl of a stand mixer fitted with the whisk attachment or with an electric mixer on medium speed, beat the egg and egg yolk until they begin to get fluffy.

5. While continuing to beat the mixture, pour the hot sugar syrup down the side of the bowl in a steady, slow stream.

6. Once the syrup is incorporated, beat in the reserved coffee mixture.

7. While continuing to beat on medium-high speed, add the butter, one tablespoon at a time, until fully incorporated into the buttercream before adding the next addition. The coffee buttercream is complete once it turns thick and fluffy.

Make the Ganache

1. Gather the ingredients.

2. In a medium saucepan over medium heat, bring the milk and cream to a boil.

3. Remove the pan from the heat and stir in the chocolate. Continue stirring the chocolate until it is melted and the mixture is smooth, about 2 minutes.

4. Add the butter and continue stirring until fully combined with the ganache.

Assemble the Cake

1. Line a large baking sheet with parchment paper. Cut one 10 x 10-inch square from both layers of cake. Place one square on the baking sheet. Set the other aside.

2. You should have two 12 x 5-inch rectangles remaining. Cut both down to 10 x 5-inch rectangles. Set aside.

3. Carefully spread 3/4 of the coffee buttercream over the surface of the cake layer on the baking sheet.

4. Lay the two 10 x 5-inch cake rectangles (so they make one 10 x 10-inch square) side by side on top of the buttercream layer. 

5. Spread the ganache over the cakes in a smooth, even layer.

6. Place the remaining 10 x 10-inch cake on top of the ganache. Spread it evenly with the remaining coffee buttercream. Chill the cake in the refrigerator for 1 hour before glazing it.

Glaze the Cake

1. Gather the ingredients.

2. Clarify the butter by melting it in a small saucepan over medium heat. Continue heating after the butter melts, skimming off and discarding any solids until you are left with a clear yellow liquid.

3. Melt the chocolate in a double boiler or in the microwave in short bursts. Whisk in the clarified butter until the glaze is smooth. Pour the chocolate glaze evenly over the entire cake.

4. Allow it to set in the refrigerator to firm up, about 1 hour. Slice off the 4 edges before serving. Enjoy.