Potatoes Del Monaco

8 or 10 potatoes cooked (boiled)
3 or 4 hard cooked eggs
1 onion chopped
1/4 lb. butter.
4 T. flour
11/2 cup milk
11/2 lb. velveeta cheese. Saute onions in butter, add flour, add milk and cheese. Cook until melted. Add chopped eggs. Put in 9x13 pan. Bake 325 30 min.