Grease slow cooker with butter or spray with a non-stick cooking spray.Place potato chunks in the slow cooker.Add broth and milk. Add garlic, salt and pepper.Cover and set to cook on low for 3 to 4 hours.When done, add sour cream and butter and mash the potatoes.Add more liquid as needed.Serve sprinkled with fresh, chopped chives, dill or parsley.