Cook your pasta noodles in salty boiling water until al dente (see package for instructions).Preheat your oven to 350F
In a large pot, melt the butter and add in the flour to create a roux. The consistency should be like loose wet sand. Cook for about 2-3 minutes occasionally stirring to prevent the flour from turning brown.
Add in your 6oz of beer.
Add in your dijon mustard. Whisk until combined.Cook for another 2-3 until the mixture is thick, whisking occasionally.
Add in milk, salt and pepper. Whisk until combined. Cook for another 2-3 minutes.
Take off the heat. Add in your cheeses, keep about a 1/2 cup of cheese for the topping. Stir the mixture until the cheese is melted and evenly combined.
Stir in your cooked pasta until combined.
Butter your 9x13 casserole dish - bottom and sides. Pour your macaroni and cheese into the dish. Try to spread it out as evenly as possible.
Top with the remainder of your shredded cheese. Bake at 350F for 30 minutes.