1/3 cup superfine sugar
1/2 cup cocoa powder
1/3 cup cake flour
1/4 teaspoon salt
8 large egg whites, at room temperature
1 teaspoon cream of tartar
1 teaspoon white vinegar
2/3 cup superfine sugar
Preheat oven to 350 degrees.
Sift sugar, cocoa, flour and salt together in a bowl.
Beat egg whites, cream of tartar and vinegar until medium stiff. Add the sugar, 1 tablespoon at the time. Beat until soft peaks form.
Fold in the dry ingredients.
Spoon into a 10-cup angel food cake pan. Smooth the top. Tap the pan on work surface to release any air pockets.
Bake about 35 minutes. Test the center of cake with a tester.
Invert cake to cool for an hour. Loosen cake with a thin spatula or a knife. Unmold and cover with egg white frosting. Decorate with chocolate shavings.