Mix all of the ingredients together except for the margarine. Place in small casserole; dot with margarine and bake at 375 degrees for about 30-40 minutes until bubbly around the edges and no longer wiggles in the middle!
P.S. I initially substituted the sour cream with 2 of those "topping" packets you get with Hamburger Helper Enchilada dinners (which is part of our snack night served with tortilla chips and Mex. condiments. (We don't like it as a topping), but it worked fine in this recipe.