Make the Joconde Sponge Cake:

1. Prepare your pans: Preheat oven to 425°F (220°C). Line three 9×13-inch baking sheets with parchment paper and lightly spray with cooking spray. This high temperature creates the characteristic thin, tender cake layers.
2. Mix the almond base: In a large bowl, whisk together almond flour, powdered sugar, and whole eggs until completely smooth and well combined. This forms the base of your batter and should be pale and fluffy.
3. Create the meringue: In a separate clean, dry bowl, beat egg whites with a pinch of salt until soft peaks form. Gradually add granulated sugar and continue beating until stiff, glossy peaks form. This meringue gives the cake its light, airy texture.
4. Combine carefully: Gently fold the sifted all-purpose flour into the almond mixture. Then fold in one-third of the meringue to lighten the batter. Add the remaining meringue in two additions, folding gently to maintain as much air as possible. Finally, fold in the melted butter until just combined.
5. Bake the layers: Divide batter evenly among the three prepared pans, spreading thin and even (about ¼-inch thick). Bake for 5-7 minutes until lightly golden and the cake springs back when touched. The cakes should be thin and delicate. Let cool completely on wire racks.

Make the Coffee Syrup:

6. Prepare the syrup: In a small saucepan, combine water and sugar. Bring to a simmer, stirring until sugar dissolves completely. Remove from heat and stir in espresso powder until dissolved. Add coffee liqueur if using. Let cool to room temperature. This syrup keeps the cake layers moist and adds essential coffee flavor.

Make the Coffee Buttercream:

7. Prepare the base: In a stand mixer, beat egg yolks on medium speed until pale and thick, about 3-4 minutes.
8. Make sugar syrup: Meanwhile, combine sugar and water in a small saucepan. Heat over medium-high until mixture reaches 238°F (soft ball stage) on a candy thermometer. This creates a stable Italian meringue base.
9. Combine carefully: With mixer running on medium speed, slowly pour hot sugar syrup into the beaten egg yolks in a thin, steady stream. Continue beating on medium-high speed until mixture cools to room temperature, about 5-7 minutes. The bowl should no longer feel warm to the touch.
10. Add the butter: With mixer on medium speed, add softened butter 2 tablespoons at a time, beating well after each addition. The mixture may look curdled initially—don’t panic! Keep beating and it will come together into silky buttercream. Once all butter is incorporated, add the dissolved espresso and vanilla. Beat until smooth and fluffy.

Make the Chocolate Ganache:

11. Create the ganache: Place chopped chocolate in a heatproof bowl. Heat cream in a saucepan until just beginning to simmer. Pour hot cream over chocolate and let sit for 2 minutes. Whisk until completely smooth and glossy. Stir in butter until melted and incorporated. Let cool slightly until spreadable but still pourable, about 10-15 minutes.

Assemble the Opera Cake:

12. Prepare layers: Trim edges of each sponge cake layer to create clean rectangles of equal size (approximately 8×12 inches). Save trimmed pieces for snacking!
13. Build the first layer: Place one cake layer on a serving platter or cake board. Brush generously with coffee syrup—the cake should be quite moist but not soggy.
14. Add buttercream: Spread half of the coffee buttercream in an even layer over the soaked cake. Use an offset spatula for smooth, professional results.
15. Second cake layer: Place second sponge cake layer on top, press gently, and brush with coffee syrup.
16. Add ganache: Spread half of the chocolate ganache in an even layer over the second cake layer. Reserve the remaining ganache for the final top layer.
17. Third cake layer: Place the final sponge layer on top, press gently, and brush with remaining coffee syrup.
18. Final buttercream: Spread remaining coffee buttercream smoothly over the top layer.
19. Final ganache coating: Refrigerate for 20 minutes to firm up the buttercream. Then spread the remaining chocolate ganache over the top in a smooth, glossy layer. For a professional finish, drag a small offset spatula or fork across the ganache to create decorative lines.
20. Chill and set: Refrigerate the assembled cake for at least 4 hours or overnight. This allows all the layers to meld together and makes slicing much easier.
21. Serve: Remove from refrigerator 20 minutes before serving for best flavor and texture. Use a sharp knife dipped in hot water and wiped clean between cuts to create beautiful, clean slices.