This luxurious frosting tops the incredible mocha dacquoise cake that Martha made to celebrate her tenth-anniversary show.
- 1 1/2 tablespoons instant espresso powder
- 2 tablespoons hot water
- 5 large egg whites
- 1 1/4 cups sugar
- 1 pound (4 sticks) unsalted butter, cut into pieces, room temperature
In a small bowl, dissolve espresso powder in 2 tablespoons hot water; set aside. In the heatproof bowl of an electric mixer, combine egg whites and sugar. Set the bowl over a pan of simmering water. Whisk constantly until sugar has dissolved and whites are hot to the touch, 3 to 5 minutes.
Transfer mixture to the bowl of an electric mixer fitted with the whisk attachment, mix on low speed, gradually increasing to high speed, until stiff, glossy peaks form, about 10 minutes.
With machine running on low speed, add butter to the egg whites, beating until smooth. Add the espresso mixture, and continue beating until incorporated.