1. Heat oven to 350 degrees F. Line a 15-1/2x10-1/2-inch jelly-roll pan with foil; lightly coat foil with vegetable cooking spray.
2. Make batter for one recipe White Cake. Spread batter evenly in prepared pan. Bake 20 minutes, until toothpick inserted in center comes out clean.
3. Cool cake in pan on large wire rack 10 minutes; invert cake onto rack. Remove pan and foil; cool completely. Repeat process with another recipe White Cake.Make Buttercream::
4. Beat the 6 tablespoons butter in large bowl with electric mixer until smooth. Add the 2 cups confectioners sugar, the 3 tablespoons heavy cream and the 1/2 teaspoon vanilla; beat until light and fluffy. Makes 1-1/3 cups.
5. Stir chopped strawberries into Buttercream. Place 1 cake layer on large platter; tuck four strips of wax paper under cake. Brush top of cake with melted jelly. Spread Buttercream over jelly; top with second cake layer.
6. Beat the 2 cups cream and the 1/4 cup confectioners sugar in large bowl on medium-high speed of electric mixer until stiff peaks form. Spread over top and sides of cake. Remove wax-paper strips. Garnish cake with sliced strawberries, blueberries and mint sprigs, if desired. Refrigerate up to 2 hours before serving. Makes 24 servings.
1. Preheat oven to 350 degrees F. Allow butter and egg whites to stand at room temperature for 30 minutes. Meanwhile, grease and lightly flour two 9x1-1/2-inch or 8x1-1/2-inch round cake pans; set aside. In a medium bowl stir together flour, baking powder, and salt; set aside.
2. In a large mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Gradually add granulated sugar, about 1/4 cup at a time, beating on medium speed until combined. Scrape sides of bowl; beat for 2 minutes more. Add egg whites, one at a time, beating well after each addition. Beat in vanilla. Alternately add flour mixture and milk to butter mixture, beating on low speed after each addition just until combined. Pour batter into the prepared cake pans, spreading evenly.
3. Bake for 20 to 25 minutes for 9-inch pans, 30 to 35 minutes for 8-inch pans, or until a wooden toothpick inserted near the centers comes out clean. Cool cake layers in pans on wire racks for 10 minutes. Remove layers from pans; cool completely on wire racks.