Ingredients

• 3 pounds Yukon Gold potatoes
• 1 1/2 cups milk
• 3/4 stick (6 tablespoons) unsalted butter
• 3 tablespoons whole-grain or coarse-grain mustard

Instructions

1. In a 5-quart kettle cover potatoes with cold salted water by 2 inches and simmer until tender, 35 to 45 minutes. While potatoes are simmering, in a small saucepan heat milk with butter over moderate heat until butter is melted. Remove pan from heat and keep milk mixture warm, covered.
2. In a colander drain potatoes and cool just until they can be handled. Peel potatoes, transferring to a large bowl. Add mustard, salt and pepper to taste, and three fourths hot milk mixture and with a potato masher mash potatoes until smooth, adding more milk mixture if necessary to make them creamy. (Potatoes may be made 1 day ahead and cooled completely before being chilled in a buttered ovenproof dish, covered. Bring potatoes to room temperature before reheating, covered.)