Sauté the vegetables: In a large pot, heat olive oil over medium heat. Add diced onion, carrots, and celery. Cook until softened, about 5 minutes. Add garlic and cook for 30 seconds until fragrant.
Add broth and seasonings: Pour in the chicken broth and water. Add Italian seasoning, salt, and pepper. Stir well and bring to a gentle boil.
Add chicken and tortellini: Stir in shredded chicken and cheese tortellini. Reduce heat and simmer for 8–10 minutes or until tortellini are tender.
Make it creamy (optional): Stir in heavy cream and Parmesan cheese for a rich, creamy version.
Add spinach and serve: Stir in baby spinach just before serving, allowing it to wilt. Serve hot with extra Parmesan and black pepper if desired.