In a medium bowl, whisk together the cream of chicken soup, gravy mix, chicken broth, garlic powder, onion powder, and black pepper until smooth.
Place the chicken breasts in the crock pot and pour the gravy mixture over the top.
Cover and cook on low for 6-7 hours, or on high for 3-4 hours, until the chicken is tender and fully cooked.
Once done, shred the chicken with two forks directly in the crock pot, or leave it whole if preferred. Stir in the sour cream (if using) to make the gravy creamier.
Serve hot over mashed potatoes, rice, or biscuits. Garnish with fresh parsley if desired.