Place garlic on a double thickness of heavy-duty foil. Drizzle with oil. Wrap foil around garlic. Bake at 425° for 15-20 minutes. Cool for 10-15 minutes.
Meanwhile, place potatoes in a small saucepan and cover with water. Bring to a boil. Reduce heat; cover and cook for 10-15 minutes or until tender. Drain. Transfer potatoes to a small bowl; squeeze softened garlic into bowl. Add the remaining ingredients; mash potatoes.