Cook the pasta in salted water according to package directions. Drain and set aside.
In a large skillet, brown the sausage over medium heat, breaking it apart as it cooks.
Add the onions, garlic, and red pepper flakes. Cook until the mixture is fragrant and the onions are softened.
Pour in the chicken broth, diced tomatoes, and Italian seasoning. Stir to combine and let the mixture simmer for a few minutes.
Stir in the cream cheese, heavy cream, and Parmesan. Continue cooking until the cheese is fully melted and the sauce is smooth.
Add the cooked pasta to the skillet and toss to coat the pasta evenly with the sauce.
Season with salt and pepper to taste.
Serve hot, garnished with parsley and extra Parmesan if desired.
Notes
After browning the sausage and before adding the broth, you can deglaze the pan with a splash of white wine or a bit of the chicken broth. This will help release any flavorful bits stuck to the bottom of the pan, adding extra depth to your soup.
Allow the soup to rest for a few minutes off the heat before serving. This helps the flavors meld together and slightly thickens the soup.
A side of crusty bread, like a baguette or ciabatta, is perfect for soaking up the rich broth, making each bite even more satisfying.