***Bring butter to room temperature.*** MISE EN PLACE: Wash (and peel, optional) potatoes; Remove skin from garlic; Grate parmesan 1) Chop potatoes into a medium pot. Add garlic and cover with water. Cook at a low boil for 15-20 minutes. Drain. 2) In a large bowl, whip potatoes with a hand mixer. Blend in parmesan, rosemary, and butter. Stir in milk. Add salt and pepper to taste.