Place the chicken breasts, chicken broth, sun-dried tomatoes, onion, garlic, Italian seasoning, salt, and pepper into the slow cooker.
Cover and cook on low for 6 hours until the chicken is fully tender.
Remove the chicken, shred it with two forks, and return it to the slow cooker.
Stir in the heavy cream, fresh spinach, and Parmesan cheese.
Cover and cook on low for 20 more minutes until the spinach wilts and the soup thickens slightly.