Opera cake components
The three building blocks of an opera cake: coffee syrup for soaking, dark ganache, and silky coffee buttercream. Make all three in one session.
Coffee syrup
Makes about 400 g.
- 240 g water (1 cup)
- 200 g granulated sugar (1 cup)
- 20 g instant espresso powder (about 2 tbsp)
- Bring the water and sugar to a boil, stirring to dissolve.
- Off the heat, whisk in the espresso powder until dissolved. Cool completely before soaking cake layers.
Chocolate ganache
Makes about 400 g.
- 200 g dark chocolate, chopped
- 200 g heavy cream
- Heat the cream to steaming. Pour over the chocolate and rest 2 minutes.
- Stir from the center outward until glossy and smooth. Cool to a spreadable consistency before layering.Watch for: If the ganache splits and looks oily, whisk in a spoonful of warm milk until it comes back together.
Coffee Swiss buttercream
Makes about 700 g.
- 150 g egg whites (about 5 large)
- 200 g granulated sugar (1 cup)
- 340 g unsalted butter, soft, cubed (3 sticks)
- 15 g instant espresso dissolved in 15 g hot water (1 tbsp)
- 5 g vanilla extract (1 tsp)
- pinch salt
- Whisk the whites and sugar in a heatproof bowl set over simmering water until 160°F and the sugar fully dissolves, 3 to 4 minutes.
- Whip to stiff, glossy peaks, then keep whipping until the bowl is room temperature, about 10 minutes.
- Beat in the butter a few cubes at a time until smooth, then the espresso mixture, vanilla, and salt.Watch for: It may look curdled halfway through adding the butter. Keep beating; it comes together.
You'll need: a small saucepan, a heatproof bowl, and a stand mixer or hand mixer.