biscuit baking mix (bisquick)
Sauté onion with margarine until softened.
In a large bowl, beat in egg.
Add milk, Bisquick, sauteed onion, 1 cup cheese.
Pour into 8 inch square pan.
Sprinkle last cup of cheese on top.
Bake at 350℉ (180℃) for about 30 minutes.
Can be prepared ahead of time and reheated at serving time.