Cook the rigatoni pasta in salted boiling water according to package instructions until al dente.
In a large skillet, crumble and cook the Italian sausage over medium heat, until browned and cooked through.
Add the diced onion to the skillet with the sausage, cooking until softened, about 5 minutes.
Stir in the minced garlic, cooking for about 30 seconds until fragrant.
Pour in the heavy cream and chicken broth, stirring to combine well with the sausage and onion mixture.
Bring the mixture to a simmer and let it cook for 5-7 minutes until slightly thickened.
Add the grated Parmesan cheese, stirring until melted and fully incorporated.
Season with salt and pepper, adjusting to your taste; then add the cooked rigatoni, tossing to coat.
If the sauce is too thick, add reserved pasta water, one tablespoon at a time, until desired consistency is reached.
Serve hot, garnished with fresh parsley and additional Parmesan if desired.
