Unsweetened cocoa powder may be substituted for cake flour in an equal weight. No more than 3 ounces (85 g) cocoa powder should be used for every 1 pound (455 g) flour. Sift in the cocoa powder with the flour. Unsweetened chocolate can be added (not substituted) at a ratio of no more than 5 ounces (140 g) per 1 pound (455 g) flour. Sweet chocolate may be added at the same rate, but the sugar should be decreased by 2 ounces (55 g) for this amount. Fold the chocolate into a small amount of the batter to temper it, then fold this into the remaining batter. Using this method, the best results are achieved with cakes containing a chemical leavening agent rather than with traditional egg-leavened sponges.
