Prepare the chicken: Place chicken breasts in a 6-quart slow cooker. Season with garlic powder, onion powder, and black pepper.
Mix the gravy base: In a medium bowl, whisk together cream of chicken soup, ranch seasoning, chicken gravy mix, and chicken broth until smooth. Pour over the chicken.
Add butter: Dot the top with butter pieces, if using, for a richer gravy.
Cook: Cover and cook on low for 6-8 hours or high for 3-4 hours, until chicken is tender.
Shred the chicken: Remove chicken, shred with two forks, and return to the slow cooker. Stir to coat in gravy.
Serve: Spoon over mashed potatoes, rice, or your favorite side. Garnish with parsley, if desired.