Preheat oven to 400 degrees. Place garlic cloves on a small square of aluminum foil and drizzle with olive oil. Wrap foil around garlic and bake in oven for 20 minutes or until golden. If you prefer, peel the potatoes. Quarter potatoes and cover with water in a large pot. Bring to a boil and simmer until tender, about 15 minutes. Drain the potatoes and return to hot pot and mash with masher or hand held mixer. Mash in the roasted garlic. Mix in butter, milk and salt and pepper. Transfer mashed potatoes to an oven proof dish and sprinkle top with parmesan. Bake in oven for 15 minutes or until top is golden.