Bring about a gallon of water to a boil in a large pot. Salt the water so it tastes like sea water.

Add the pasta and cook until al dente. Drain and set aside.

Melt the butter in pot over medium heat. Cook the butter until it takes on some brown color, but not black.

Stir in the flour and dry mustard. Cook for about a minute, stirring constantly.

Then add the milk.

Bring the milk mixture to a boil and cook for 1 minute, stirring regularly. Slowly add the cheese, stirring until it completely melts.

Mix the cheese and the pasta together.

Preheat your oven to 350 degrees.

Choose a cast iron skillet. Just before cooking, spray the cast iron with cooking oil, or put a few drops of oil in the center and rub in it with a paper towel. This should help prevent sticking.

Add the mac & cheese to the skillet. Smooth it out with a spatula so it is in an even layer.

Bake in the oven for 25 to 35 minutes, until the cheese has browned.

Remove carefully from the oven and serve.