Season chicken breasts on both sides with Italian seasoning, onion powder, salt, and pepper.
Spray the crockpot with nonstick cooking spray. Layer the seasoned chicken breasts in the bottom of the crockpot.
In a bowl, whisk together chicken broth, heavy cream, minced garlic, sun-dried tomatoes, and Parmesan cheese.
Pour the sauce mixture over the chicken in the crockpot. Set the crockpot to cook on high for 3 hours or low for 5 hours.
Once the chicken is cooked, add chopped spinach to the crockpot.
Taste and adjust seasoning with additional salt and pepper, if needed.
Serve over pasta, rice, or with bread on the side.