Before you begin cooking, ensure all your vegetables are chopped and minced as specified in the ingredients list. This will make the cooking process smoother.

Heat the olive oil in a large Dutch oven or soup pot over medium-high heat. Add the Italian sausage, breaking it up with a wooden spoon or spatula, and cook until thoroughly browned and no pink remains, about 8-10 minutes. Drain any excess fat from the pot and transfer the cooked sausage to a separate bowl. Set aside.

Reduce the heat to medium. Add the chopped onion, carrots, and celery to the same pot (add a splash more olive oil if needed). Cook, stirring occasionally, until the vegetables are softened, about 6-8 minutes.

Stir in the minced garlic and cook for another minute until fragrant.

Sprinkle the all-purpose flour over the vegetables and stir continuously for 1-2 minutes, allowing it to cook and form a roux.

Gradually whisk in the chicken broth, making sure to scrape the bottom of the pot to loosen any browned bits. Add the diced tomatoes (undrained), dried Italian seasoning, salt, and black pepper. Bring the soup to a gentle simmer.

Return the cooked sausage to the pot. Reduce the heat to low, cover, and let the soup simmer for 15 minutes to allow the flavors to meld and the vegetables to become fully tender.

Stir in the heavy cream until fully combined. Add the fresh spinach, a handful at a time, allowing each batch to wilt into the soup before adding more. Continue to stir until all the spinach has completely wilted, about 2-3 minutes.

Taste the soup and adjust seasonings (salt and pepper) if necessary.

Ladle the hot soup into bowls and serve immediately, garnished with a generous sprinkle of grated Parmesan cheese.