In 4- to 5-quart slow cooker, place potatoes, chicken broth and butter.
Cover; cook on High heat setting 4 hours to 4 hours 30 minutes or until potatoes are tender.
Add remaining ingredients except milk. Mash, crush or smash potatoes using potato masher, or beat with electric mixer on low speed until well blended. Do not overmix. Stir in enough milk for desired creamy consistency. Cover and keep warm on Low or Warm heat setting until serving time, up to 2 hours. Stir before serving.