Opera Cake

Make the coffee buttercream by combining 80g granulated sugar and 60ml water in a small saucepan, bring to a boil over medium-high heat, and cook without stirring until the syrup reaches 118°C (245°F) on a candy thermometer.

While the syrup cooks, beat the 4 egg yolks in a stand mixer on medium speed until pale and thick; with the mixer running, carefully pour the hot sugar syrup in a slow, steady stream down the side of the bowl and beat until the mixture is thick and cooled to room temperature, about 5 minutes.

Add the softened butter to the egg yolk mixture one tablespoon at a time, beating well after each addition until a smooth, fluffy buttercream forms, then beat in the espresso mixture and mix until fully incorporated; set aside at room temperature.

Make the chocolate ganache by heating 120ml heavy cream in a small saucepan over medium heat until just simmering, then pour it over 150g chopped dark chocolate in a heatproof bowl; let sit for 2 minutes, then stir until completely smooth and glossy; stir in 15g butter until melted; allow to cool until spreadable, about 20 minutes.

To assemble, place the first sponge rectangle on a flat tray or cutting board lined with parchment; brush generously with coffee syrup until thoroughly moistened.

Spread an even layer of coffee buttercream approximately 4mm thick over the first soaked sponge layer using an offset spatula.

Place the second sponge rectangle on top, press gently, and brush again with coffee syrup; spread the chocolate ganache in an even 4mm layer over this second layer.

Place the third sponge rectangle on top, press gently, and brush with the remaining coffee syrup; spread the remaining coffee buttercream in a thin, smooth layer over the top.

Refrigerate the assembled cake for at least 30 minutes until the layers are firm and set.

Prepare the chocolate glaze by heating 80ml heavy cream until simmering, pouring it over 100g chopped dark chocolate, letting it sit for 2 minutes, stirring until smooth, and stirring in 20g butter; allow to cool to 35°C (95°F) until pourable but not hot.

Remove the chilled cake from the refrigerator and pour the chocolate glaze over the top, spreading quickly with an offset spatula to create a perfectly smooth, mirror-like surface; work quickly as the glaze sets fast.

Return the cake to the refrigerator for at least 1 hour or until fully set; when ready to serve, use a sharp knife dipped in hot water and wiped dry to trim the edges cleanly and cut into neat portions; serve chilled.