In a medium bowl, stir together flour, sugar, baking powder and baking soda. Using a pastry blender, cut in butter (or margarine) until the mixture resembles coarse crumbs. Combine buttermilk and egg product (or egg). Add to the flour mixture all at once, stirring just until mixture is moistened. On a lightly floured surface, pat the dough to 1/2-inch thickness. Cut the dough with a floured 2-1/2-inch star-shaped or heart-shaped cookie cutter or a round biscuit cutter, rerolling scraps as necessary. Place shortcakes on the prepared baking sheet. Bake for 8 to 10 minutes or until golden. Cool the shortcakes slightly on a wire rack.