Combine potatoes and chicken broth in a slow cooker.
Cook potatoes on Low for 3 hours. Add cauliflower and continue cooking on Low another 3 hours.
Stir milk, butter, sour cream, black pepper, garlic powder, paprika, and salt into the potato mixture. Mash with a potato masher or blend with an immersion blender to desired consistency.
Continue cooking until hot, about 10 minutes more.