Gluten-Free Opera Cake

Ingredients

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• 1 1/2 cups (150 g) finely ground almond flour Shop
• 1 1/4 cups (150 g) powdered sugar, for the sponge Shop
• 4 large whole eggs, at room temperature
• 1/4 cup (35 g) gluten-free all-purpose flour blend Shop
• 4 large egg whites, at room temperature, for the sponge
• 2 tbsp granulated sugar, for the sponge Shop
• 2 tbsp unsalted butter, melted and cooled
• 1/2 cup hot strong brewed coffee or espresso
• 1/4 cup granulated sugar, for the syrup Shop
• 2 large egg whites, for the buttercream
• 1/2 cup granulated sugar, for the buttercream Shop
• 3/4 cup (1 1/2 sticks) unsalted butter, softened, for the buttercream
• 1 tbsp instant espresso powder, dissolved in 1 tsp hot water Shop
• 8 oz bittersweet chocolate (60-70%), finely chopped
• 3/4 cup heavy cream

Instructions

1. 1 Preheat the oven to 425°F (220°C). Line a 12x17-inch half-sheet pan with parchment and grease the paper.
2. 2 For the sponge, beat the almond flour, powdered sugar and whole eggs on high for 5 minutes, until pale and thick. Fold in the gluten-free flour blend.
3. 3 In a clean bowl, whip the 4 egg whites to soft peaks, add 2 tbsp sugar and whip to firm, glossy peaks. Fold the whites into the almond mixture in two additions, then fold in the melted butter. Spread evenly in the pan.
4. 4 Bake for 7-9 minutes, until light golden and springy. Cool for 5 minutes, run a knife around the edges, and turn the sponge out onto parchment. Cool completely, then cut it crosswise into three 12x5 1/2-inch strips.
5. 5 For the syrup, stir the hot coffee with 1/4 cup sugar until dissolved. Cool.
6. 6 For the ganache, heat the cream until steaming, pour it over the chocolate, wait 2 minutes and stir until smooth. Set aside 1/2 cup for the glaze and let the rest cool until thick enough to spread, about 30 minutes.
7. 7 For the buttercream, whisk the 2 egg whites and 1/2 cup sugar in a heatproof bowl over simmering water until the sugar dissolves and the mixture reaches 160°F (71°C). Whip on high until stiff and cool, about 8 minutes. Beat in the butter a tablespoon at a time, then the dissolved espresso, until smooth.
8. 8 Place one sponge strip on a board and brush it generously with syrup. Spread with half the buttercream. Top with the second strip, brush with syrup, and spread with the thickened ganache. Add the last strip, brush with syrup, and spread with the remaining buttercream in a thin, smooth layer. Chill for 1 hour.
9. 9 Warm the reserved ganache until just pourable, about 90°F (32°C), and pour it over the top, spreading it to the edges. Chill for at least 2 hours, then trim the edges with a hot, dry knife and cut into 12 slices.

Tips & Notes

• Bake the joconde sponge only until it springs back. It is very thin, and an extra minute makes it too dry to soak up the coffee syrup.
• Spread each layer of the opera cake thin and even, and chill between steps if the buttercream starts to soften. Neat, flat layers are what give the classic striped slice.
• Use a long knife dipped in hot water and wiped dry for every cut. It slices cleanly through the chocolate glaze without cracking it.

Common questions