Heat olive oil in a large pot, add sausage, and cook until browned. Remove and set aside.
In the same pot, sauté onion until softened, then add garlic and cook for 1-2 minutes.
Add chicken broth and diced tomatoes, bring to a boil, then reduce to a simmer for 10 minutes.
Stir in heavy cream, spinach, Parmesan, and sausage. Simmer until spinach wilts, 5-10 minutes.
Season with salt and pepper. Serve hot with extra Parmesan on top.
