Cook the pasta according to package directions. Drain and set aside.
In a large skillet, heat olive oil over medium-high heat. Add sausage and cook until browned, breaking it apart.
Add chopped onion and cook for 3–4 minutes until softened. Stir in garlic and cook another 30 seconds.
Season with Italian seasoning, salt, and pepper. Stir in heavy cream and chicken broth. Bring to a simmer.
Stir in Parmesan cheese and let it melt into the sauce.
Add cooked pasta, spinach, and sun-dried tomatoes. Stir everything together and simmer for 2–3 minutes.
Serve hot, garnished with extra Parmesan if desired.