Heat a large pot over medium heat, then add the butter or oil, celery, carrots, onion, salt, and a few cracks of black pepper. Cook for about 10 minutes until softened and translucent, stirring every couple minutes to make sure the vegetables don’t brown.
Add the chicken broth, bring the soup to a boil, then reduce to a simmer over medium low heat.
Add the tortellini and spinach, stir for 2-3 minute to wilt, then stir in the shredded chicken.
Let simmer on low-medium heat for about 10 minutes and serve with parmesan cheese.