In a large pot, heat the olive oil over medium heat. Add the diced chicken and cook until browned, about 5-7 minutes. Remove the chicken from the pot and set aside.
In the same pot, add the chopped onion, garlic, carrots, and celery. Sauté until the vegetables are softened, about 5 minutes.
Stir in the diced tomatoes, chicken broth, and the cooked chicken. Bring to a simmer.
Add the cannellini beans, spinach, oregano, basil, salt, and pepper. Simmer for an additional 10-15 minutes, allowing the flavors to meld together.
Taste and adjust seasonings if necessary.
Serve hot, topped with grated Parmesan cheese and fresh basil leaves for garnish.