French Opera Cake

Step 1

Preheat oven to 375°F. Line a 9x13 inch baking pan with parchment paper.

Step 2

Whisk almond flour and all-purpose flour together in a small bowl.

Step 3

Beat egg yolks with 0.5 cup sugar until pale and thick, ~3 minutes.

Step 4

Fold flour mixture into yolk mixture until just combined. Stir in 4 tbsp softened butter.

Step 5

Beat egg whites until soft peaks form. Gradually add remaining 0.25 cup sugar; beat until stiff peaks form.

Step 6

Fold whites into batter in two additions until no streaks remain.

Step 7

Pour batter into prepared pan. Bake until a toothpick comes out clean, 20-25 minutes.

Step 8

Cool cake completely on a wire rack, ~30 minutes. Level to 1/2 inch if needed with a serrated knife.

Step 9

Beat 6 tbsp softened butter with powdered sugar until light and fluffy, ~2 minutes.

Step 10

Dissolve espresso powder in 1 tbsp hot water. Stir into buttercream until evenly colored.

Step 11

Heat cream until steaming. Pour over chopped chocolate; let sit 1 minute, then stir until glossy.

Step 12

Cool ganache to room temperature, ~15 minutes, until it coats the back of a spoon.

Step 13

Spread half the buttercream evenly over the cooled cake layer.

Step 14

Pour ganache over buttercream. Spread gently with an offset spatula until smooth.

Step 15

Refrigerate at least 2 hours, or up to 24 hours, until set. Cut into 8 squares with a warm knife.