Prepare a plain white sauce by mixing 1 tbs. flour into 1 tbs. melted butter. Cook for a minute until the mixture is bubbly. Then pour in 1 cup milk & cook over low heat, stirring constantly until sauce comes to a boil and thickens. Continue to cook for 1 minute to all raw flour flavor.
If you want cheese sauce just add 1 cup grated cheese a little at a time to the suace & stir until melted. Season with salt & pepper if you want to. This will store for a day or two in refrigerator. Good over vegetables or pasta.