Place potatoes and onion in a 6-qt. slow cooker; add broth, garlic, salt and pepper. Cook, covered, on low 8-10 hours or until potatoes are tender., Mash potatoes to desired consistency. Stir in cream cheese, cream and butter. Cook, covered, 15 minutes longer or until heated through., Just before serving, whisk soup to combine. Top servings with bacon, cheese and chives.