Place the chicken thighs in the bottom of the slow cooker. Add the diced onion, sliced carrots, cubed potatoes, minced garlic, and chopped sun-dried tomatoes on top.
Pour the chicken broth over the ingredients. Sprinkle in the Italian seasoning, salt, and black pepper.
Cover and cook on low for 6 to 7 hours or on high for 3 to 4 hours until the chicken is tender and the vegetables are soft.
Remove the chicken thighs, shred them with two forks, and return the meat to the slow cooker.
Stir in the heavy cream until the broth turns creamy. Add the fresh spinach and stir until it wilts, about 2 minutes.
Ladle into bowls and top with grated Parmesan cheese before serving.