Prepare the vegetables: Dice the carrots, celery, and onion. Mince the garlic.
In the crockpot, add the chicken breasts, diced carrots, diced celery, diced onion, and minced garlic.
Pour the chicken broth over the ingredients in the crockpot.
Stir in the dried thyme, dried basil, salt, and black pepper.
Cover and cook on low for 6 hours or on high for 3 hours.
After the cooking time is up, remove the chicken breasts from the crockpot and shred them using two forks.
Return the shredded chicken to the crockpot, and add the gnocchi and heavy cream. Stir to combine.
Let the soup cook for an additional 30 minutes on high, or until the gnocchi are cooked through and tender.
Stir in the fresh spinach just before serving, allowing it to wilt for a couple of minutes.
Serve hot, garnished with grated Parmesan cheese if desired.