Scrub potatoes with vegetable brush under cold running water. Peel. Cut into–inch cubes. Place in large saucepan and add cold water to cover. Over high heat, bring to boiling. Reduce heat to medium. Cover and simmer until potatoes are very tender, about 18 to 20 minutes. Drain.
While potatoes are cooking, cut the top third off the garlic head. Wrap garlic head in foil and bake until very tender, 45 minutes. Remove from oven and let cool 10 minutes. Squeeze garlic from skins into small bowl and mash with a fork. Set aside.
Return potatoes to saucepan and mash with a potato masher until smooth. Whisk together the reserved garlic, milk, oil, rosemary, salt and pepper. Stir into potatoes until blended.
Nutritional Analysis per serving: 154 calories 3 g protein, 23 g carbohydrates, 6 g fat, 1 g saturated fat (33% of calories from fat), 2 mg cholesterol, 2 g fiber, 35 mg sodium.