Preheat your oven to 400°F (200°C). Line an 18x13 inch baking sheet with parchment paper. Lightly grease the parchment.

In a large bowl, combine almond flour, powdered sugar, and whole eggs. Beat with a stand mixer fitted with a whisk attachment on high speed for 5-7 minutes until light, fluffy, and tripled in volume.

Gently fold in the sifted all-purpose flour, then the cooled melted butter until just combined. Be careful not to deflate the mixture.

In a separate clean bowl, whip egg whites with granulated sugar until stiff peaks form.

Gently fold one-third of the egg white mixture into the almond mixture to lighten it, then fold in the remaining egg whites until no streaks remain. Be very gentle.

Evenly spread the batter onto the prepared baking sheet. Bake for 8-10 minutes, or until lightly golden and springs back when gently touched. Avoid overbaking.

Immediately invert the biscuit onto a clean sheet of parchment paper or a wire rack, peel off the baking parchment. Let it cool completely. Once cool, trim the edges to form a neat rectangle and cut the biscuit into three equal 8x12 inch rectangles.

In a small saucepan, combine water and granulated sugar. Bring to a simmer over medium heat, stirring until sugar dissolves. Remove from heat.

Stir in the instant espresso powder until dissolved, then add the coffee liqueur (if using). Let cool completely.

In a small saucepan, combine 1/2 cup granulated sugar and 1/4 cup water. Bring to a boil over medium heat, without stirring, until the syrup reaches 240°F (115°C) on a candy thermometer.

While the syrup is heating, beat egg yolks in the bowl of a stand mixer on medium-high speed until light and thick.

Once the sugar syrup reaches 240°F (115°C), immediately and carefully pour the hot syrup in a thin, steady stream into the beaten egg yolks with the mixer running on medium-low speed. Avoid hitting the whisk.

Increase speed to high and continue beating for 8-10 minutes until the mixture is very thick, pale, and completely cooled to room temperature.

Reduce speed to medium-low and add the room temperature butter, piece by piece, incorporating each piece before adding the next. The mixture may look curdled at first, but keep beating until it comes together and becomes smooth and creamy.

Stir in the vanilla extract and dissolved espresso powder. Beat until combined and fluffy. Set aside.

Place chopped dark chocolate in a heatproof bowl. In a small saucepan, heat heavy cream until it just begins to simmer. Pour the hot cream over the chocolate.

Let stand for 5 minutes, then whisk gently from the center outwards until smooth and glossy. Let cool at room temperature until it thickens to a spreadable consistency (about 30-60 minutes).

Place one joconde biscuit layer on your serving platter or a flat board. Brush generously with coffee syrup until well moistened.

Spread half of the coffee buttercream evenly over the biscuit layer.

Carefully place the second joconde biscuit layer on top. Brush generously with coffee syrup.

Spread the chocolate ganache evenly over the second biscuit layer.

Place the third joconde biscuit layer on top. Brush generously with coffee syrup.

Spread the remaining coffee buttercream evenly over the third biscuit layer. Chill the cake in the refrigerator for at least 1 hour to firm up the layers.

Place chopped dark chocolate, butter, and neutral oil in a heatproof bowl set over a saucepan of simmering water (bain-marie). Stir occasionally until completely melted and smooth.

Remove from heat and let cool slightly until it's lukewarm but still pourable. The ideal temperature is around 90-95°F (32-35°C).

Remove the chilled cake from the refrigerator. If using a cake frame, remove it now. Place the cake on a wire rack set over a tray to catch drips.

Pour the lukewarm chocolate glaze over the entire cake, spreading quickly and evenly with an offset spatula to cover the top and sides. Let excess drip off.

Carefully transfer the cake to a clean serving platter. Chill for at least 3-4 hours, or preferably overnight, for the glaze to set completely and for the flavors to meld.

Before serving, trim the edges again for a very clean presentation. Decorate with a stencil and cocoa powder, or a small chocolate 'Opera' inscription if desired.