Bring a large pot of salted water to a boil.
Add potatoes, garlic and chicken bouillon cubes.
Cook potatoes until tender but still firm, about 15 minutes.
Drain, reserving a little of the cooking water. Mash potatoes with sour cream and cream cheese, adding reserved cooking water to reach desired consistency.
Transfer to a 4 quart crockpot, cover, and cook on low for 2 to 3 hours. Just before serving, stir in butter and season with salt and pepper to taste.