Melt butter in a saucepan over medium heat; stir in flour, salt, and pepper until smooth, about 5 minutes. Slowly pour milk into butter-flour mixture while continuously stirring until mixture is smooth and bubbling, about 5 minutes. Add Cheddar cheese to milk mixture and stir until cheese is melted, 2 to 4 minutes. Fold macaroni into cheese sauce until coated. Footnotes. You can never have enough cheese, and I usually add an extra half cup without ruining the recipe. Keep a careful eye on the milk when boiling, as milk boils fast and burns easily. Burnt milk will show up in the recipes flavor if overcooked. Aluminum foil helps keep food moist, ensures it cooks evenly, keeps leftovers fresh, and makes clean-up easy.