Melt fat (butter, margarine, or drippings) in a small saucepan over low heat and blend in flour to form a smooth paste. Gradually stir in milk and heat, stirring constantly until thickened and smooth. Add seasonings, then let mellow about 5 minutes over lowest heat. Note: If sauce is to be held a short while (up to 20-25 minutes), transfer to the top of a double broiler, set over simmering water, and cover. To hold longer, remove from heat, place a circle of wax paper flat on sauce (to prevent a skin from forming), and cool to room temperature; refrigerate until needed. Reheat in the top of a double broiler.