Warm milk in microwave or sauce pan until lukewarm. Melt butter in small saucepan, but do not brown. Stir in the flour, salt and pepper and allow to bubble for about a minute on medium to low heat. Do not let it brown. Remove from heat and gradually whisk in the warm milk. Return to heat and whisk or stir constantly over medium to medium high heat just until it boils. Lower heat to medium low and continue to stir for one minute. This makes a perfect, non-lumpy, medium white sauce! To make thin sauce, reduce amount of flour and butter to 1 Tbsp each. For a thicker sauce, increase flour and butter to 3 tablespoons each.