Meanwhile, with portable electric mixer, beat egg whites until stiff; set aside. With same beater, beat yolks until thick and lemon colored. Slowly add sugar, beating constantly. Add flour, beating just until blended. Stir into chocolate mixture. With rubber scraper or wire whisk, gently fold chocolate mixture into beaten egg whites. Turn into prepared pan. Reduce oven temperature to 350 degrees. Bake for 25 minutes. Let cool completely in pan on wire rack; cake will settle like a cheesecake. Refrigerate until well chilled, about 4 hours.

To serve: Loosen cake; remove from pan by inverting on serving plate. If desired, decorate with Chocolate Curls. Cut cake into 3/4 inch slices. Makes 16 servings.