Prep the slow cooker. Lightly grease the insert or use a liner.
This helps prevent sticking and makes cleanup easy.
Layer the chicken. Place the chicken breasts (or thighs) in a single layer at the bottom. If the pieces overlap a little, that’s fine.
Mix the seasoning base. In a bowl, whisk together the chicken broth, ranch seasoning, garlic powder, onion powder, and black pepper. Pour this mixture over the chicken.
Add the dairy. Cut the cream cheese into cubes and scatter it over the chicken.
Add the butter if using. Hold the sour cream or Greek yogurt until the end to avoid curdling.
Set and cook. Cover and cook on Low for 4–5 hours or High for 2.5–3 hours, until the chicken is cooked through and easily shreds. Thighs may finish slightly sooner and stay juicier.
Shred the chicken. Transfer the chicken to a plate and shred with two forks.
It should pull apart without much effort.
Finish the sauce. Whisk the sauce in the slow cooker until smooth. Stir in the sour cream or Greek yogurt. Return the shredded chicken and stir to coat.
Taste and add salt if needed.
Serve and garnish. Spoon the ranch chicken over rice, noodles, or potatoes, or pile it on a toasted roll. Top with chopped parsley or chives for freshness.