Cook pasta per package directions for al dente, drain and set aside.
In a medium saucepan, over medium heat, melt butter and then stir in flour.
Pour heavy whipping cream into the pan and stir until combined.
Add Parmesan cheese, stir until melted and add salt and pepper.
Add pasta water to cheese sauce, stir.
Add cooked pasta to cheese sauce, stir to combine.
Pour pasta and cheese sauce into the prepared baking dish followed by the sausage mixture on top.
Sprinkle with mozzarella cheese and bake uncovered for 20 minutes or until the cheese is hot and bubbly.
Serve with a side salad and garlic bread.