Name: Opera Cake
Cook time: P0Y0M0DT3H0M0.000S
Total time: P0Y0M0DT4H15M0.000S
Yield: 8 to 12 servings
Cuisine: french
Ingredients: 3 large whole eggs plus 3 large egg whites, at room temperature; 1 cup superfine almond flour (see Cook's Note; 1 teaspoon vanilla bean paste; 1/4 teaspoon kosher salt; 3/4 cup sugar; 1/2 cup all-purpose flour (see Cook's Note); 2 tablespoons unsalted butter, melted and cooled slightly; 3 tablespoons espresso powder; 2 tablespoons sugar; 1/2 cup heavy cream; 1 cup chopped bittersweet chocolate (about 6 ounces); 4 large egg yolks, at room temperature; 1 cup sugar; 1 3/4 sticks (14 tablespoons) unsalted butter, cubed, at room temperature; 1 teaspoon vanilla bean paste; 1/2 teaspoon kosher salt; 1 tablespoon espresso powder; 1 cup chopped bittersweet chocolate (about 6 ounces); 1 tablespoon refined coconut oil

Directions

Special equipment:

a candy/deep-fry thermometer, a stand mixer and whisk attachment

For the almond sponge cake: Preheat the oven to 375 degrees F and line a rimmed baking sheet with parchment.
Whisk the 3 whole eggs, almond flour, vanilla bean paste, salt and 1/2 cup of the sugar in a large bowl until well combined; set aside. Meanwhile, beat the 3 egg whites with the remaining 1/4 cup sugar in a stand mixer fitted with the whisk attachment on medium-high speed until fluffy, shiny and holds stiff peaks, 2 to 4 minutes.
With a clean spatula, gently fold half the egg-white mixture into the almond-flour batter until just incorporated, making sure to not overmix and deflate the egg whites. Fold in the remaining egg-white mixture until just combined. Sift the all-purpose flour through a fine-mesh sieve over the batter and gently fold to combine. Finally, pour the melted butter around the perimeter of the bowl, then fold until fully incorporated.
Pour the batter into the prepared rimmed baking sheet, then smooth into an even layer with an offset spatula. Bake until the cake has puffed, is just cooked through and springs back when gently pressed on the surface, 12 to 14 minutes. Cool on the baking sheet for 5 minutes, then run a paring knife around the perimeter of the baking sheet to loosen the edges of the cake. Invert onto a wire rack, gently remove the parchment and let cool completely. The cake should be thin (about 1/4 inch thick).
For the espresso soak: While the cake is cooling, stir together 1/2 cup warm water, the espresso powder and sugar in a medium liquid measuring cup until the sugar has dissolved. Set aside.
For the bittersweet chocolate ganache: Warm the cream in a small saucepan over medium heat until just simmering, about 2 minutes. Place the chopped chocolate in a medium bowl, then pour over the warm cream. Let sit until the chocolate has softened, about 2 minutes, then stir with a rubber spatula until completely smooth. Set aside until cooled to room temperature (it will thicken but should still be spreadable).
For the coffee French buttercream: Beat the egg yolks in a stand mixer fitted with a whisk attachment on medium-high speed until pale yellow and thick, about 5 minutes.
Meanwhile, place the sugar and 1/4 cup water in a medium saucepan over medium heat. Attach a candy/deep-fry thermometer to the side of the pan and bring to the soft-ball stage (240 degrees F), swirling the pan every so often, 4 to 5 minutes.
Reduce the mixer to medium speed and slowly drizzle in the hot syrup, aiming the syrup between the side of the bowl and the beaters. Once all the syrup has been incorporated, increase the speed to medium-high and continue to whip until both the bottom of the bowl and the mixture are cool, about 10 minutes. The mixture should be thick but will not form a peak at this point.
While still beating on medium-high speed, add the cubed butter, a few pieces at a time, and beat until firm peaks, 1 to 2 minutes. As the butter is added, the buttercream may appear to thin out some, but it will thicken into firm peaks once all the butter is added. Beat in the vanilla bean paste and salt. Dissolve the espresso powder into 1 tablespoon water, then add to the buttercream. Beat until just combined, about 1 minute. Set aside at room temperature until ready to assemble.
To assemble the cake, cut the almond sponge cake crosswise into thirds (each about 6 by 13 inches). Place one cake layer on a long serving platter. Brush the cake with one-third of the espresso soak. Spread half of the ganache over the cake with an offset spatula into a smooth, even layer, making sure to go all the way to the edges. Spread about 3/4 cup of the buttercream over the ganache, also into a smooth, even layer. Top with another layer of cake, then brush with another one-third of the espresso soak. Then spread on the remaining ganache and 3/4 cup buttercream. Top with the third and final layer of cake and brush with the remaining espresso soak. Spread the remaining buttercream all over the top and sides of the cake, making it as smooth as possible (this will ensure the glaze will be as smooth as possible). Refrigerate until the cake is chilled through and the buttercream and ganache has become firm, at least 1 hour and up to overnight.
For the chocolate glaze: Fill a small saucepan with 1/2 cup water and bring to a simmer over medium heat. Place the chopped chocolate and coconut oil in a medium heatproof bowl, then place the bowl over the simmering water (make sure the bottom of the bowl doesn't touch the water). Stir the chocolate with a rubber spatula until completely melted and smooth, 2 to 3 minutes. Remove from the heat and place in a large liquid measuring cup. Cool until it’s no longer piping hot, about 5 minutes.
Remove the cake from the refrigerator. Working quickly, pour over the glaze in a smooth, thin layer; it will set quickly on the chilled cake. Use an offset spatula to smooth out the sides if any drips do not fully cover the buttercream. Return to the refrigerator to set, about 10 minutes.
To serve, run a serrated knife under warm water for 30 seconds, then dry with a clean kitchen towel (this will give you a clean slice). Cut crosswise into 1-inch-thick slices, moving slowly so the chocolate glaze doesn’t crack. Serve immediately or refrigerate slices in an airtight container for up to 3 days.

Cook’s Note

We prefer superfine (also known as finely ground) store-bought almond flour for this recipe; it’s not only easily accessible, but it also provides a super light and fluffy texture in the sponge. When measuring flour, we spoon it into a dry measuring cup and level off excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.)