Place the chicken breasts in the slow cooker. Add the chicken broth, minced garlic, Italian seasoning, salt, and black pepper.
Scatter the chopped sun-dried tomatoes over the chicken.
Cover and cook on low for 6 hours or until the chicken reaches an internal temperature of 165°F.
Remove the chicken from the slow cooker and set it aside on a plate. Stir the heavy cream and Parmesan cheese into the remaining liquid in the slow cooker until the sauce is smooth.
Add the fresh spinach to the sauce and stir until it wilts, about 2 minutes.
Return the chicken to the slow cooker and turn it to coat with the sauce before serving.