Heat oven to 400. Wrap whole garlic bulb tightly in foil. Put garlic and potatoes in oven. Bake garlic 45 minutes or until soft when squeezed. Remove and let cool. Continue baking potatoes until tender when pierced, about 15 minutes.
Unwrap garlic and squeeze pulp from bulb into a 4-qt pot. Peel 3 of the hot potatoes, add to garlic in pot and mash until nearly smooth. Gradually stir in chicken broth and pepper until blended. Place over medium heat and cook until hot, stirring occasionally. Meanwhile, cut remaining potatoes (with skin) in 3/4-inch pieces. Stir into soup and cook until heated through. Serve with some or all accompaniments.