1. Heat olive oil in a large pot or Dutch oven over medium heat. Add diced chicken and cook until no longer pink, about 5-7 minutes. Remove chicken and set aside. Add onion, carrots, and celery to the pot. Cook until softened, about 5-7 minutes. Add minced garlic and cook for 1 minute more until fragrant. Return cooked chicken to the pot. Stir in chicken broth, diced tomatoes, Italian seasoning, salt, and pepper. Bring to a boil, then reduce heat, cover, and simmer for 15 minutes to allow flavors to meld. Add tortellini to the soup and cook according to package directions, usually 3-5 minutes, until al dente. Stir in spinach until wilted, about 1-2 minutes. If desired, stir in heavy cream for a richer soup. Taste and adjust seasonings as needed. Serve hot, garnished with freshly grated Parmesan cheese.