Preheat oven to 400°F. Cook macaroni according to package and set aside.
In a large saucepan or Dutch oven, melt butter. Stir in flour, dry mustard and black pepper. Cook for about 1-2 minutes until well combined. Gradually add milk and cook until the mixture is smooth and bubbly, about 10 minutes. You'll want to stir constantly.
Remove sauce from heat and gradually add 4 cups of sharp cheddar cheese and whisk until cheese is melted and smooth.
Add pasta and mix until everything is coated. Pour half of the mac and cheese into a 9x13 greased baking dish or 12 inch cast iron skillet. Add 2 cups of cheese evenly throughout and then the remaining mac and cheese. Top with remaining 2 cups of cheese.
Bake for 20-25 minutes or until cheese is golden brown and bubbly. Remove from heat and let cool for 5 minutes before serving.
Notes
No overcooked pasta – Cook the macaroni al dente according to the package instructions. The pasta will finish cooking in the oven while it’s in the sauce.
Freshly grated cheese – Don’t use pre-shredded cheese. It doesn’t taste as good and also has addition ingredients that you don’t need.
Stir constantly – Once the milk is added, you must stir constantly as it heats up and becomes thick. Otherwise you’ll have burnt milk on the bottom.
Lots of sauce – Who likes a dry macaroni and cheese? At first when making this, you’ll think it is too much sauce but believe me when that the macaroni soaks it up.
Create layers – You’ll notice only have of the cheese goes in the sauce. When preparing the macaroni and cheese, you add only half of the pasta to the baking dish then 2 cups of cheese. You then add the remaining half of the pasta before topping with the remaining cheese.