The oven should be heated at 425degF (220degC). Prepare a baking sheet by covering it with parchment paper to ensure that the cake doesn't stick.
Create the Joconde The Joconde: In a large bowl beat the eggs with powdered sugar until they're thin and pale. Then, mix in the regular flour and almond flour. After that, gently stir with the butter that has been melted until all is well blended.
Distribute the Joconde batter evenly over the baking sheet. Bake for 8-10 minutes, until lightly golden. Cool it down before cutting in layers.
For the coffee ganache, Warm the heavy cream until it reaches a boil. Serve it with the chocolate pieces in the bowl. Allow it to rest for a couple of minutes to melt. Stir till it's completely smooth. You can add the coffee liqueur if you're looking to add a little flavor!
Coffee buttercream by beating your softened butter to it becomes creamy. Gradually add the powdered sugar and the coffee you brewed making sure it is it is smooth and fluffy.
Now, assemble your Opera Cake! In a mould that is rectangular place the Joconde. Infuse each layer with coffee syrup or brewed coffee. Spread an ganache layer over the top, followed by the buttercream layer. Repeat the procedure until the entire mould is placed in the mold.
Serve your cake with chocolate glaze on the top. Cool in the refrigerator for several hours before cutting and serving.