Heat the olive oil in a large pot or Dutch oven over medium heat. Add the Italian sausage and cook, breaking it up with a spoon, until browned and cooked through, about 5 to 7 minutes. Remove excess grease if needed.

Add the onion, carrots, and celery to the pot. Cook for 4 to 5 minutes, stirring occasionally, until the vegetables begin to soften.

Stir in the garlic and cook for 30 seconds until fragrant.

Pour in the chicken broth and diced tomatoes, then add the Italian seasoning, salt, and black pepper. Bring the soup to a boil.

Reduce the heat to medium-low and simmer for 10 minutes, allowing the flavors to blend and the vegetables to become tender.

Add the gnocchi and cook according to package instructions, usually 2 to 4 minutes, until they float to the top and are tender.

Stir in the spinach and cook just until wilted, about 1 minute.

Lower the heat and stir in the heavy cream and Parmesan cheese. Taste and adjust seasoning with more salt and pepper if needed.

Ladle into bowls and serve warm with additional Parmesan cheese if desired.