Place the chicken breasts in the bottom of your slow cooker.
In a mixing bowl, combine the cream of chicken soup, chicken broth, dry onion soup mix, garlic powder, and black pepper. Pour this mixture over the chicken in the slow cooker.
Cover and cook on low for 6-8 hours, or until the chicken is cooked through and tender.
Around 30 minutes before serving, mix the cornstarch with water to create a slurry. Add this to the slow cooker and stir well to combine. This will help thicken the gravy.
Cover and cook on high for an additional 30 minutes until the gravy has thickened.
Serve the chicken and gravy hot, garnished with fresh parsley if desired
