Chop onions and garlic, then crush fennel seeds.
Sauté fennel and onions in olive oil over medium heat for about six minutes until tender.
Remove casings from sausages and crumble them into the pot.
Cook sausages for around seven minutes until browned.
Add garlic, crushed fennel seeds, red pepper flakes, salt, and black pepper; cook for another minute.
Pour in white wine and bring to a boil.
Add heavy cream, half-and-half, and tomato paste; bring back to a boil and then simmer for 20 minutes.
Cook rigatoni in salted boiling water for 14 minutes.
Drain pasta and add it to the sauce, cooking together for five minutes.
Stir in parsley and half a cup of Parmesan cheese before serving.
