Based on TGirl,RN's Creamy Macaroni & Cheese for One (#88172), which is delicious. I have adapted it to feed a larger group. Be aware that measurements on seasonings are a rough estimate, as I am a 'taste and tweak as I go' kind of cook. You can adjust, as I have, to suit your personal palate.
This will make one very full 9 x 13" baking dish, which is probably enough to feed 6 people as a main dish, or even more as a side dish. Would probably be good for a potluck crowd, too. If doing that I would try to bake it at the party, if possible, so the topping stays crispy.