1/4 lb. butter
2 onions
1/4 c. flour
3-4 c. milk
8 med. potatoes
6-8 thick slices Velveeta cheese

Melt butter, add flour - mix thoroughly over medium heat. Gradually add milk, stirring constantly until it thickens. Add cheese, stirring constantly. Salt and pepper to taste. Place sliced potatoes and onions into greased casserole. Pour sauce over the top. Bake at 350 degrees for 1-1 1/2 hours.