2 tbsp. butter
2 tbsp. all-purpose flour
1 tsp. salt
1 c. milk
1 c. cheese, grated
2 c. cold boiled or baked potatoes, cubed

Preheat oven to 400 degrees. Melt butter. Add flour and salt. Stir until well blended. Add milk gradually, stirring constantly. When thickened, add grated cheese. Remove from heat. Place potatoes in a greased shallow baking dish. Cover with sauce. Bake 30 to 40 minutes. Serves 4.