Melt the margarine in a skillet and saute the onions until tender. In a bowl combine the sour cream, salt, parsley and half cup cheese. Combine and add to the onion mixture and set aside. Combine the muffin mix, egg, milk, corn and hot sauce and mix well. Spread in a greased 9 x 23 cm pan. Cover with the sour cream mixture. Top with the remaining cheese. Bake in a 425 degree oven for 25 to 30 minutes