Place unpeeled whole potatoes in a 6 quart slow cooker. Pour chicken broth on top. Cover and cook on high for 4 hours or until fork tender. (Tip: Cut any larger potatoes in half so they're all similar size)
Do not drain. Using an electric hand mixer or a potato masher, mash the potatoes with the broth until chunky smooth. (Use a mixer for a smoother texture and a potato masher for a chunky texture.)
Add cream cheese, sour cream, butter, Ranch dressing mix and black pepper to taste. Whip until fully incorporated.
Add 1 cup cheese, bacon and green onion. reserving 2 Tbsp each crumbled bacon and onion to garnish the top. Mix well.
Sprinkle the top with remaining cheese. Garnish with bacon and onion. Keep warm until serving.