Using an electric mixer, beat margarine, masa and sugar together until light and fluffy, about 10 minutes.
stir in cornmeal, salt, milk and remaining 2 cups corn
Cover tightly with aluminum foil. Steam in a large stovetop steamer or in oven. To steam in oven, place pan inside roasting pan. Pour very hot tap water inside roasting pan to a depth of 1 inch. Steam for 1 hour and 15 minutes or until knife comes out clean, stirring after 15 minutes and after 45 minutes. Keep tightly covered until ready to serve.