Preheat the oven to 375 degrees F
To a large pot of boiling salted water and a little oil drizzled in, cook pasta according to the directions on the package, taking off 1 or 2 minutes to cook al dente. 6 to 8 minutes. Reserve about 1/4 cup pasta water and set aside before draining well.
Meanwhile, grate cheese to desired amount. At least 2 cups to add to sauce and 1 cup to put on top.
Heat the milk and half and half in a small saucepan, but don't boil it.
In a large saucepan or dutch oven, melt butter and add diced onions over medium low to medium heat. Saute for 5 to 7 minutes until onions are translucent. Add chopped garlic the last 1 or 2 minutes. Stir.
Add flour, cook over medium low heat for 2 minutes, stirring with a whisk. While whisking, add the hot milk and cook for a minute or two more, until thickened and smooth.
Add seasonings, Hot sauce, ground mustard, pepper, nutmeg and stir. Add reserved pasta water. Stir.
Off the heat, add at least 2 cups of the cheeses. Stir. Add the cooked macaroni and stir well. Fold the macaroni into the cheese sauce. combine thoroughly and pour into a 3-quart baking dish. Top with remaining cheese.
Bake for 25 to 35 minutes, or until the sauce is bubbly and the macaroni is browned on top. Allow to cool slightly before serving. The cheese can burn the roof of your mouth.
To freeze: Allow to come to room temperature before wrapping tightly in plastic wrap and placing in a zip lock bag or airtight container. Keeps well frozen for 2 months. Let thaw overnight in the refrigerator before reheating.