1. 1. Brown the Sausage: Heat the olive oil in a large pot or Dutch oven over medium-high heat. Add the Italian sausage, breaking it up with a spoon as it cooks. Continue to cook until the sausage is fully browned and no pink remains, about 5-7 minutes. Drain off any excess grease from the pot.

2. 2. Saute Aromatics: Add the chopped yellow onion to the pot with the cooked sausage. Saute for 3-4 minutes until the onion softens and becomes translucent. Stir in the minced garlic and cook for another minute until fragrant, being careful not to burn the garlic.

3. 3. Simmer the Broth: Pour in the chicken broth and add the undrained diced tomatoes. Stir in the dried Italian seasoning, salt, and black pepper. Bring the mixture to a gentle boil, then reduce the heat to a simmer. Let it simmer for about 10 minutes to allow the flavors to meld together.

4. 4. Add Tortellini: Carefully add the refrigerated tortellini to the simmering soup. Cook according to package directions, usually 3-5 minutes, until the tortellini is tender but still firm to the bite. Avoid overcooking, as it can make the tortellini mushy.

5. 5. Stir in Cream and Spinach: Remove the pot from the heat. Stir in the heavy cream until fully combined, giving the soup its rich, creamy texture. Add the fresh spinach and stir gently until it wilts into the hot soup, which should only take about 1-2 minutes.

6. 6. Taste and Serve: Taste the soup and adjust seasonings if necessary, adding more salt or pepper to your liking. Ladle the hot soup into bowls and garnish generously with grated Parmesan cheese before serving.