Fourth of July Berry Shortcake Supreme

Preheat oven to 450 degrees. Grease and flour an 8 inch round cake pan. Stir together flour, sugar, baking powder and salt in a large bowl. Add egg, milk and margarine and mix until evenly moistened. Scrape batter into the prepared pan and bake 12 to 15 minutes until golden brown. Transfer pan to a rack and cool 10 minutes. Remove shortcake from pan and cool completely. Meanwhile, stir together marshmallow creme, 2 tbsp. cream and vanilla in a medium bowl. Beat remaining cream to stiff peaks in a large bowl. Fold in marshmallow creme mixture. Split shortcake in half crosswise. Fill with half of marshmallow creme mixture and half of berries. Top shortcake with remaining marshmallow creme and berries.