Heat olive oil in a large pot over medium heat.
Add sliced sausage and cook until browned, about 3 minutes.
Stir in diced onion and garlic, cooking until softened.
Pour in chicken broth, heavy cream, and diced tomatoes.
Add pasta, Italian seasoning, salt, and pepper. Stir to combine.
Bring to a boil, then reduce heat and simmer for 15 minutes, stirring occasionally.
Once pasta is tender, remove from heat and stir in cheddar and Parmesan cheese.
Let sit for 2 minutes until cheese is melted, then garnish with parsley and serve.