Heat butter in a large saucepan over medium low heat. Whisk in flour, stir until absorbed.
3
Heat milk in microwave 1 minute to warm, do not let boil. Add to pan stirring constantly with a whisk until no lumps. Season with salt and pepper. Cook sauce over medium heat until thickened.
4
Add all but 1/2 cup of cheddar cheese to the sauce. Stir until cheese is melted. Remove from heat and fold in macaroni. Serve topped with remaining cheddar cheese.