Combine potatoes, chicken broth, onion, butter, salt, and pepper in a slow cooker (such as Crock Pot(R)). Cook on High until soup flavors meld and potatoes are extremely soft, 4 to 5 hours.
Stir bacon, half-and-half, Cheddar cheese, and sour cream into the soup. Turn heat to Low setting; cook until thick and creamy, 15 to 20 minutes more.
Mash the soup in the slow cooker using a potato masher to your desired consistency. Garnish with additional Cheddar cheese, sour cream, and chives.