Sprinkle with half of the cheese, dot with half of the butter, and sprinkle with half of the salt.
Repeat the layers using the remaining macaroni, remaining cheese, remaining butter, and remaining salt.
Pour milk evenly over top.
Cover with aluminum foil, and refrigerate overnight (about 12 hours, or up to 24 hours).
Bake, covered with foil, at 350°F (180°C) for approximately 45 minutes. Remove the foil during the final 10 minutes to allow top to brown. For a really crispy top, place the dish under the broiler for a couple of minutes at the end.
Refrigerate the casserole for about 24 hours before baking, allowing the noodles to soften as they soak in the milk. At a minimum, let the noodles soak for at least 8-12 hours.
Start with blocks of cheese that you grate yourself at home, rather than using bags of pre-shredded cheese from the store. The pre-shredded cheese includes stabilizers and other ingredients to prevent the cheese from clumping, which inhibits its ability to melt smoothly in the dish.
If you prefer acrispier, darker brown top on your mac and cheese, place the dish under the broiler during the final minute or two of baking.
Use a combination of just about any flavorful melting cheeses that you prefer. For instance, try Velveeta (American), Colby or Colby-Jack, Gruyere, Pepper Jack or Monterey Jack, gouda, smoked gouda, Swiss or mozzarella. The options are endless, so pick your favorites!
Add toasted breadcrumbs (like these) to the top of the dish after you remove the cover during the final 10 minutes.
Bulk up the meal with vegetables like frozen peas or broccoli. If using a firm vegetable like broccoli, it's best to parboil or steam the broccoli before adding it to the dish.
Add meat such as crispy bacon, leftover ham, or shredded, cooked chicken.
Cooking for a smaller family? Cut all of the ingredients in half and bake the casserole in an 8-inch square dish.