beginning to thicken. Sift flour and baking powder over eggs and fold in. Gradually fold in chocolate mixture. Transfer batter to prepared pan. Bake cake 20 minutes. Cover pan with foil. Bake until tester inserted into center comes out with moist crumbs still attached, about 30 minutes longer. Uncover cake; cool in pan on rack (cake will fall as it cools.) (Can be made 1 day ahead. Cover; let stand at room temperature.) Cut around pan sides to loosen cake. Release pan sides. Sift powdered sugar over cake; cut into wedges. ----