Heat a standard waffle iron and spray with cooking spray. In a mixing bowl, combine flour, sugar, walnuts, baking powder, cornstarch, cinnamon, salt, ginger, and nutmeg. Mix well. Stir in egg yolks, pumpkin, milk, and margarine. Mix until moistened; set aside. In another mixing bowl, beat egg whites until soft peaks form. Gently fold into pumpkin mixture. Pour enough batter onto hot waffle iron, or filling two-thirds of the waffle iron. Bake for four minutes, or as directed from your waffle iron instructions.