To convert a cake recipe that uses bittersweet or semisweet chocolate to one using cocoa: (information taken from Rose Levy Beranbaum's Cake Bible) Substitute 1 tablespoon plus 1 3/4 teaspoons…
½ cup cocoa powder 1 ¼ cup buttermilk (divided use) 1 ¼ cup granulated sugar 2 large eggs, separated (divided use) ¾ cup butter (divided use) 1 cup light brown…