Heat oven to 350~. Spray 13x9" baking pan with vegetable cooking spray. In large bowl, stir together flour, cocoa, cornstarch, baking powder, baking soda and salt. In medium bowl, with wire whisk, stir sugar and water. Add egg whites and corn syrup, beat with whisk until blended. Gradually add liquid mixture to flour mixture, stirring with whisk until smooth. Stir in mashed banana. Pour batter into prepared pan. Bake 30-35 minutes or until wooden pick inserted in center comes out clean. Cool in pan on wire rack. Cut cake into 12 squares, slice each square in half horizontally. Place slice banana between cake layers. Top each piece with 1 tablespoon Chocolate sauce. Garnish with whipped topping and cherry, if desired. makes 12 servings. CHOCOLATE SAUCE: In medium saucepan, stir together sugar, water and corn syrup. Cook oven medium heat, sitrring frequently, until mixture boils,boil about 1 minute. Remove from heat, stir in cocoa and vanilla. Cool slightly. Makes about 1 cup sauce. ----