1. Cut off pointed end of garlic; place garlic on a piece of aluminum foil. Fold foil to seal.
2. Bake at 400° for 1 hour, and let cool 10 minutes. Squeeze pulp from garlic bulb; discard husk, and set pulp aside.
3. Bring potatoes and cold water to cover to a boil in a large Dutch oven; boil 25 minutes or until tender. Drain. Place back in Dutch oven, and heat 3 to 5 minutes over low heat until potatoes are dry. Set aside.
4. Heat whipping cream in a small saucepan over low heat 4 minutes or just until warm; remove from heat, and stir in sour cream.
5. Press potatoes through a ricer into Dutch oven. Let stand 1 minute. Stir in roasted garlic pulp, melted butter, salt, and pepper until blended. Gradually stir in warm whipping cream mixture, stirring just until blended. Serve immediately.