Yield a 8''x10''/20x28cm cake. An opéra cake is a French dessert noted for its delicate, intensely flavored layers. There are many stories about the origins of this cake, known as both Clichy cake and Opéra cake, believed to have started out at the Paris Exposition Culinaire in 1903. However, another pastry shop, Dalloyau in the 50s, sold a very similar dessert (in honor of the Paris Opéra) although Gaston Lenôtre claims he invented the opéra cake as well. Whoever did it, this amazing cake will stick around for many years to come!. A traditional opera cake is made of thin layers of almond sponge cake (biscuit Joconde) that are completely soaked in coffee syrup. Buttercream and ganache should be equally distributed and thinly layered. The cake must then be glaze with semi-hard dark chocolate coating but never finished with mirror glaze. Its height should not go higher than 1.2''https://bruno.b-cdn.net/3cm. If you have never tried Opéra cake make sure you'll get it from the right patisserie. Indeed, only a handful chefs really know how to make it right. Otherwise, make it!..Opéra can be refrigerated for up to 5 day or frozen for weeks.
Makes two 18''x13''/46x33cm baking trays lined with greased parchment or silicon mat. In a mixing bowl, beat room temp egg whites and one-third of the sugar on high speed. Continue beating to firm peaks adding remaining sugar gradually. Transfer meringue in a separate bowl. No need to clean the mixing bowl. Gather almond meal with powdered sugar, flour and eggs on high speed for 5 min on high speed. Fold in one-third of the meringue first and add remaining meringue and the melted butter. Spread Joconde batter evenly using a large offset spatula.
Bake at 450ºF/230ºC for about 7 min using a convection oven or 10 min in conventional oven. Do not over bake the biscuit Joconde sheet or it will lose its flexibility. Let cool to room temp, wrap up and refrigerate.
(Crème Anglaise Based). Bring milk, sugar and coffee beans to a simmer. Turn off the heat, cover and let infuse for an hour or more. Meanwhile in a separate bowl, mix egg yolks and sugar. Once milk is infused, bring back to a boil, remove from heat and whisk in the yolk mixture gradually. Return custard to the stove, gently heat up the mixture to 185ºF/85ºC, stirring constantly. Immediately remove from the heat and pass through a sieve that is set over a the mixing bowl (discard coffee beans). Beat the crème Anglaise on high with the whisk attachment. Add instant coffee and beat until it cools down to room temperature. Add the softened butter and beat to smooth. Buttercream can be kept refrigerated for a week or kept frozen for up to 3 months. Thaw, rewarm to room temp, and beat prior reusing it.
Gently melt chocolate. Meanwhile, warm up heavy cream with corn syrup. Combine both mixtures and stir until completely smooth. Throw in butter and smooth out. Let ganache to set prior using. Can be made a day ahead and left at room temperature overnight.
Chablon: in French (chablonner un biscuit) which means coaitng the surface of a sponge with chocolate to reenforce the foundation of a cake keeping its moisture in. Melt chocolate and mix in oil.
*Coffee extract or 5 espresso or more to taste (reduce amount of water is using espresso). Bring all ingredients to boil and let cool to room temp before using. Can be stored 2 weeks in the refrigerator.
Use an upside down 9''x12''https://bruno.b-cdn.net/23x30cm baking tray or something similar. Divide each cake sheet in half and make two 9''x12''/23x30cm rectangles; save 3 sponge sheets for the opera cake and save the last one for backup. For the chablon, with an offset spatula coat the surface of one sponge with the melted chocolate (for the bottom). Cover immediately with parchment in contact and flip; refrigerate to set. Remove from the fridge and brush generously with the coffee syrup (each layer of sponge must be well soaked in coffee syrup; that’s one of the main characteristic of the opéra cake and where everyone fails).
Carefully, spread 1/3 of the coffee buttercream over the surface of the first sponge; it should not exceed 0.14''/3.5mm thickness. Each layer of the cake should have the same thickness. Cover with the second sponge, brush with coffee syrup and spread the chocolate ganache evenly. Place the third and the last sponge cake on the top the ganache and moisturized with coffee syrup. Chill cake until firm and spread evenly the third and the last coffee buttercream layer. To even the top cake perfectly, heat up a long offset spatula and run over the buttercream to smooth out. Place opera cake the refrigerator overnight (do not freeze before glazing or condensation will appear on the surface).
Melt all ingredients together over a water-bath until the mixture reaches 120ºF/50ºC. Cool to 95º/35/36ºC before using. Once the opéra cake is glazed, save chocolate glaze that has dropped on the bottom, rewarm it, strain it and store for later use.
Line a baking tray with plastic wrap (to save dripping glaze). Transfer cake on a cooling rack and a place over it. Get the opera glaze ready at 95ºF/35/36ºC and transfer glaze into a loaf pan (barely larger than the cake) and spread chocolate glaze over the cake from left to right in a slow but regular motion. Tap the tray to remove any air bubbles and immediately run a large offset spatula on the surface of the just glazed cake; 6 o'clock to noon and noon to 6. This will remove excess chocolate glaze creating an awesome thin and barely firm top notch finish. Refrigerate opera cake to set. Trim off sides and serve whole or cut into rectangles. To make cuts look sharper, fill up a pitcher of hot water and dip the blade in between cuts, and wipe off. Decorate with a touch a gold leaf if desired. Enjoy!