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 shells
1/4 cup onion, minced finely
2 tbsp. dijon mustard
melt butter, mix in flour slowly...add mild a little at a time and whisk.
when a thick consistency, mix in the cheeses, cheddar first and only 3/4 of all of the cheese.
add 1/2 of macaroni to a buttered pan and pour 1/2 of the mixture over the mac. then add the rest of the mac and the other half of the cream sauce.
Let set for 5 mins. then top off with the rest of the cheese and a little bit of bread crumbs if you wish...if you are looking for true decadence, scatter small crumbs of butter on top
Bake for 25 mins at 350 until brown on top.
Hope you like this recipe....it is a variation on Joy of Cooking...very good.