Follow the package instructions to cook pasta until it is just al dente. Drain.
Butter melt in a large skillet on medium heat while pasta is cooking. Cook garlic until fragrant for 1-2 minutes. Mix in flour.
Mix in the chicken broth and then add half and half.
Stir in salt, pepper, cayenne and red pepper flakes. Let sauce simmer for 5 minutes.
Mix in 1 cup mozzarella cheese and Parmesan cheese until smooth.
Cut the sausage into pieces of 1/4 inch and add them to the sauce along with the chopped parsley, cooked pasta, and the chopped parsley. Add salt and pepper to taste.
Preheat broiler. Place the pasta mixture in a 9x13 inch, lightly greased baking dish. Top with remaining mozzarella cheese.
Broil for 2 to 3 minutes or until cheese is golden and bubbly.
