
Cook your pasta according to the instructions but save a cup of the pasta water (this helps thicken later)
Cook the sausage in a skillet and set aside
Add onion to soften (about 5 minutes) in the same skillet you cooked the sausage. Add butter after onions softened and add mushrooms. Cook another 5 minutes
Add the sausage to the onions and mushrooms and stir. Add the milk and the cup of reserved water from pasta. Add all seasonings, stir, and boil until thickened, stirring occasionally.
Stir in the pasta and stir in the cheese until creamy. Start with a cup but add more if needed. If it's too creamy, add a little more milk.
Serve and sprinkle a little parm on top if desired