Let’s break down the process into detailed stages:

1. Make the Joconde Sponge:

• Preheat oven to 425°F (220°C). Line a baking sheet (e.g., half-sheet pan) with parchment paper.
• (Standard Joconde Method Recommended): Separate 3-4 of the eggs. Whip the egg whites with a pinch of salt and a small amount of granulated sugar until stiff peaks form. Set aside.
• In a separate large bowl, beat the remaining whole eggs and egg yolks (if separated) with the powdered sugar until pale and ribbony.
• Gently fold in the almond flour and all-purpose flour.
• Fold in the melted butter.
• Gently fold the whipped egg whites (if separated) into the batter in thirds. Do not overmix.
• Spread the batter thinly and evenly onto the prepared baking sheet.
• Bake for 8-10 minutes, until lightly golden and set. Watch carefully, it bakes quickly.
• Let cool completely, then carefully peel off the parchment paper. Trim the edges and cut the sponge into 3 equal rectangular layers (size depends on your mold or desired final cake shape).

2. Make the Coffee Syrup:

• Dissolve sugar and instant coffee (if using) in hot water. Let cool completely. If using strong brewed coffee, you might just add sugar to taste.

3. Make the Coffee Ganache:

• Place chopped dark chocolate in a heatproof bowl.
• Heat heavy cream in a saucepan until just simmering. Pour hot cream over the chocolate. Let stand for 2-5 minutes.
• Whisk gently until smooth and glossy. Stir in coffee liqueur, if using. Let cool slightly until spreadable but still fluid.

4. Make the Coffee Buttercream:

• In a stand mixer with the paddle attachment (or using a hand mixer), beat the softened butter until very creamy and pale.
• Gradually add the powdered sugar, beating on low speed until incorporated, then increasing speed to medium-high until light and fluffy.
• Beat in the cooled brewed coffee until smooth and fully combined.

5. Assemble the Opera Cake:

• Place one layer of Joconde sponge in the bottom of your rectangular mold (if using) or directly on your serving platter/cardboard base.
• Brush the sponge generously with the cooled coffee syrup.
• Spread half of the coffee ganache evenly over the soaked sponge. Chill briefly (10-15 min) to help set.
• Spread half of the coffee buttercream evenly over the ganache layer.
• Place the second layer of Joconde sponge on top. Brush generously with coffee syrup.
• Spread the remaining coffee buttercream evenly over the second sponge layer. Chill briefly.
• Place the third layer of Joconde sponge on top. Brush generously with coffee syrup.
• Spread the remaining coffee ganache evenly over the third sponge layer. Chill the cake thoroughly (at least 1-2 hours, or until firm).

6. Make the Chocolate Glaze:

• (Simple Version): Gently melt the dark chocolate and butter together over a double boiler or in the microwave in short bursts, stirring until smooth. Let cool slightly until it’s fluid but not hot (around 90°F/32°C is often ideal for pouring).

7. Glaze the Cake:

• Remove the very cold cake from the mold (if used). Place it on a wire rack set over a baking sheet (to catch drips).
• Pour the slightly cooled chocolate glaze over the top of the cake, allowing it to run down the sides. Use an offset spatula to quickly smooth the top if necessary. Work quickly as the glaze will set on the cold cake.
• Let the glaze set completely (you can chill it again briefly). Trim the edges with a hot, sharp knife for clean lines if desired. Traditionally, “Opera” is written on top with leftover glaze or chocolate.

8. Final Chill and Serve: * Chill the cake for at least another hour or two before serving to allow the flavors to meld and the cake to firm up for slicing. Serve chilled or slightly cooler than room temperature.

This requires patience and precision!