Flourless Chocolate Espresso Cake
This recipe is excerpted from "Martha Stewart's Cakes" (Clarkson Potter, September 2013; $25).
- 3 tablespoons unsalted butter, plus more for cake pan
- 6 ounces bittersweet chocolate, preferably 70 percent cacao, chopped
- 6 large eggs, separated, room temperature
- 1 cup sugar, divided
- 3 tablespoons instant-espresso powder
- 1/4 teaspoon coarse salt
- 1 tablespoon pure vanilla extract
- Chocolate Glaze
Preheat oven to 350 degrees. Invert bottom of a 9-inch springform pan (so cake will slide easily onto serving plate) and line with a parchment round; butter parchment. Melt butter and chocolate, stirring until smooth, in a bowl set over a saucepan of simmering water.
Beat together egg yolks and 1/2 cup sugar with a mixer on medium-high speed until thick and pale, about 3 minutes. Add espresso powder and salt; beat until combined, about 1 minute. Add vanilla and melted-chocolate mixture; beat about 1 minute more.
In another bowl, beat egg whites on medium-high speed until foamy. Increase speed to high; gradually add remaining 1/2 cup sugar, beating until stiff peaks form, about 5 minutes. Fold into chocolate mixture in 3 batches. Transfer batter to pan and bake until set, 40 to 45 minutes. Let cake cool completely in pan on a wire rack. Remove side of pan; transfer cake to a serving plate. Serve glaze alongside cake.