Beat egg, add flour,baking powder,salt and pepper and onion into large bowl. Stir the mashed potatoes into this mixture.
Drop big spoonfuls(however big you want them) onto hot skillet, with about 3-4 tablespoons melted butter, margarine or oil. Brown on both sides. Sometimes I serve them with a small dollop of sour cream and a sprinkle of chopped green onions.