Arrange blueberries in upper left corner of cake, creating a 4x5 inch rectangle. Arrange strawberries in rows for red stripes. 12 to 15 servings. VANILLA BUTTERCREAM FROSTING: In large bowl, combine powdered sugar and butter. Add milk and vanilla; beat to spreading consistency. About 2 cups.JM Hershey's is a registered trademark of Hershey Foods Corporation. Recipe may be reprinted courtesy of the Hershey Kitchens. ----