Place the chicken breasts in the bottom of the slow cooker.
In a mixing bowl, combine the ranch dressing mix, cream of chicken soup, sour cream, garlic powder, onion powder, salt, and pepper. Mix until well combined.
Pour the creamy mixture over the chicken in the slow cooker, ensuring the chicken is well coated.
Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is cooked through and tender.
About 30 minutes before serving, shred the chicken using two forks and stir in the shredded cheddar cheese. Cover and let the cheese melt.
Serve warm, garnished with fresh parsley if desired.