Opera Cake

Ingredients

• 3 large eggs
• 3 large egg whites
• 90g almond flour
• 90g powdered sugar, sifted
• 30g all-purpose flour
• 20g unsalted butter, melted
• 30g granulated sugar for egg whites
• 120ml strong brewed espresso, cooled
• 30g granulated sugar for coffee syrup
• 15ml dark rum
• 4 egg yolks
• 80g granulated sugar for buttercream
• 60ml water
• 200g unsalted butter, softened, for buttercream
• 2 teaspoons instant espresso powder dissolved in 1 tablespoon hot water
• 150g dark chocolate (70% cocoa), finely chopped for ganache
• 120ml heavy cream for ganache
• 15g unsalted butter for ganache
• 100g dark chocolate (70% cocoa), finely chopped for glaze
• 80ml heavy cream for glaze
• 20g unsalted butter for glaze

Instructions

1. Preheat the oven to 220°C (425°F) and line a 30x40cm (12x16 inch) rimmed baking sheet with parchment paper, then lightly grease it with butter.
2. In a large bowl, whisk together the almond flour, powdered sugar, whole eggs, and all-purpose flour until smooth and slightly thickened, about 3 minutes.
3. In a separate clean bowl, beat the egg whites with an electric mixer until foamy, then gradually add 30g granulated sugar and beat to stiff, glossy peaks.
4. Gently fold one-third of the beaten egg whites into the almond batter to lighten it, then carefully fold in the remaining egg whites in two additions, preserving as much volume as possible.
5. Fold in the melted butter until just combined, then spread the batter evenly onto the prepared baking sheet in a thin, uniform layer.
6. Bake for 5 to 7 minutes until the sponge is just set, lightly golden, and springs back when touched; do not overbake or it will crack when rolled.
7. Remove the sponge from the oven and let it cool completely on the pan, then carefully cut it into three equal rectangles approximately 10x20cm each.
8. Prepare the coffee soaking syrup by combining 120ml brewed espresso with 30g granulated sugar in a small saucepan over medium heat, stirring until the sugar dissolves completely, then remove from heat, stir in the rum, and let cool.
9. 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.
10. 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.
11. 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.
12. 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.