For a high-altitude version of this cake, see here.

Prepare Angel Food Cake. Substitute ½ cup (40g) unsweetened cocoa powder, preferably Dutch-process, for ½ cup (50g) of the sifted cake flour. If desired, dissolve in the 1 tablespoon water (1 teaspoon instant espresso powder), then add it to the egg whites. Fold into the batter with the last addition of cocoa and flour 2 ounces (55g) semisweet or bittersweet chocolate, finely chopped or grated.