I know that a recipe was posted before, but I am a cuisiniere, so I will post my own, which I make once a week, especially for my hard-core mac n cheese bf...
3tbsp. of butter
2 or 2 and a half tbsp. of flour
1 cup of hot milk
2 cups cheddar
1/2 cup gruyere
3/4 regular box of macaroni...or...