Preheat oven to 350°F. Toss garlic with olive oil in baking pan. Cover with foil; bake 30 minutes. Uncover; bake until garlic is tender, about 15 minutes. Cool; peel and chop.
Cook potatoes in large pot of boiling salted water until tender, about 25 minutes. Drain. Transfer potatoes to large bowl. Add garlic and remaining ingredients. Using electric mixer, beat mixture until smooth. Season to taste with salt and pepper. Can be prepared 2 hours ahead. Cover; let stand at room temperature. Rewarm, stirring constantly, before serving.