Preheat oven to 400°F (200°C). Line a 17¼x12¼-inch rimmed baking sheet with parchment paper, letting excess extend over sides of pan.

In a medium heatproof bowl, sift together almond flour and confectioners’ sugar. Add eggs, one at a time, whisking until well combined after each addition. Place bowl over a saucepan of simmering water; cook, whisking frequently, until an instant-read thermometer registers 95°F (35°C) to 105°F (41°C). Remove from heat, and whisk by hand until light and ribbon- consistency. (Alternatively, beat with a hand mixer at medium-high speed until light and ribbon-consistency.)

In the bowl of a stand mixer fitted with the whisk attachment, beat egg whites and cream of tartar at medium speed until foamy. With mixer on medium speed, add granulated sugar in a slow, steady stream; increase mixer speed to medium-high, and beat until medium-stiff peaks form.

Add almond flour mixture to egg white mixture, and very gently fold until almost combined. (Mixture should look streaky.) Sift cake flour over egg mixture, and gently fold until just combined. Transfer about 1 cup (75 grams) batter to a small bowl, and fold in melted butter and vanilla. Return mixture to large bowl, and fold until just combined. Pour large dollops across prepared pan, and gently spread into an even layer using as few strokes as possible.

Bake until golden and firm to the touch, 8 to 9 minutes. Let cool in pan for 10 minutes. Using excess parchment as handles, remove from pan, and let cool completely on parchment on a wire rack.

Move cake to a cutting board, and trim edges to create a 15x10½-inch rectangle. Discard edges. Cut into 3 (10½x5-inch) rectangles. Peel off parchment paper, and discard parchment. (Do not start soaking cake layers or assembling cake until syrup, buttercream, and ganache recipes are prepared and ready to be used.)

In a small microwave-safe bowl, heat chocolate on high for 30 seconds; stir chocolate. Heat on high in 15-second intervals, stirring between each, just until chocolate is melted.

Place 1 cake layer on a medium cutting board. Spread melted chocolate into an even layer on top of rectangle, being careful not to push it off cake onto cutting board. Refrigerate until firm, 5 to 10 minutes.

Turn cake layer so chocolate is on bottom. Place Coffee Syrup in a squeeze bottle, and soak cake layer with syrup. (If you do not have a squeeze bottle, use a pastry brush to soak cake layer.) Place half of Espresso French Buttercream (about 1 cup or 200 grams) into a pastry bag fitted with an extra-large ribbon piping tip (Ateco #898). (This is to make it easier to get an even layer of buttercream. If you do not have a ribbon tip, you can dollop and spread buttercream into an even layer.)

With flat side of piping tip facing up, pipe an even layer of buttercream on top of soaked cake layer; using a small offset spatula, smooth any lines. Place remaining Espresso French Buttercream in pastry bag, and set aside. Place second cake layer on top of buttercream layer, making sure it is even with bottom, and soak with Coffee Syrup. Dollop Ganache on top, and spread into an even layer. Top with remaining cake layer, and soak with Coffee Syrup. Pipe remaining buttercream on top, and smooth flat. Place a piece of parchment paper on top of buttercream. Refrigerate until firm, about 1 hour, or freeze until firm, about 30 minutes.

Discard parchment. Place 2 tablespoons (30 grams) Chocolate Glaze into a parchment piping bag. (See step 5 of The Assemblage.) Quickly pour remaining Chocolate Glaze over cold buttercream, tapping and lifting cutting board to help it settle and smooth out. (It is OK if some drips down the sides.) Let stand until set, 5 to 7 minutes. Cut a very small opening in tip of parchment piping bag, and pipe “Opera” onto cake (and designs, if desired). Let stand until set, 5 to 7 minutes.

Using a hot dry knife, trim edges, cleaning knife between cuts. Cut into 6 slices. Serve immediately. (If not serving right away, cover and refrigerate for up to 5 days until ready to serve and then trim and slice. Let stand at room temperature to soften buttercream.)