Season the Chicken: Coat both sides of the chicken breasts with Italian seasoning, onion powder, salt, and pepper.
Prepare the Slow Cooker: Lightly spray the inside of the crockpot with nonstick cooking spray and place the seasoned chicken inside.
Make the Sauce: In a mixing bowl, whisk together chicken broth, heavy cream, minced garlic, sun-dried tomatoes, and Parmesan cheese.
Cook: Pour the sauce over the chicken, cover, and cook on high for 3 hours or low for 5 hours until the chicken is tender.
Add Spinach: Stir in the chopped spinach just before serving, cover, and let it wilt for a few minutes.
Serve & Enjoy: Taste and adjust seasoning if needed. Serve over pasta, rice, or with crusty bread.