In a large pot of salted water, cook noodles as directed on the package. Reserve ½ cup of pasta water when noodles are almost cooked. Strain and set aside.
Meanwhile, in a large pan, add butter, milk, salt, pepper, and ground mustard and heat on low. Continue to cook until butter is melted. Turn off the heat.
Add cooked noodles to the milk and butter mixture and stir. Add cheese on top of noodles but don’t stir. Let sit for 2-3 minutes and then stir until cheese is melted. If cheese is not melting well after 2 minutes, add a couple tablespoons of the pasta water and stir.
Serve and enjoy!
Note - cheese melts better if it is taken out of the refrigerator about 10 minutes before adding to the pan.