If desired, sear the chicken breasts in olive oil over medium heat for 2 to 3 minutes per side until golden brown. This step is optional.
In the slow cooker, combine the cream of chicken soup, ranch seasoning mix, chicken broth, garlic powder, onion powder, and black pepper. Stir until smooth.
Add the chicken breasts to the slow cooker and coat well with the sauce.
Cover and cook on low for 6 to 7 hours or on high for 3 to 4 hours, until the chicken is cooked through and shreds easily.
Shred the chicken directly in the slow cooker with two forks and stir it into the sauce.
Stir in the sour cream until combined. Add shredded cheddar and fresh parsley to garnish, if using, and serve warm.
Notes
Searing the chicken before slow cooking adds extra flavor but is optional. Store leftovers in the fridge for 3 to 4 days or freeze for up to 3 months. Reheat gently in a skillet with a splash of broth to loosen the sauce.