Peel potatoes, and cut into 1/2-inch-thick slices. Place in a medium stockpot, and cover with cold water. Add 2 tablespoons salt. Place over high heat, and bring to a boil. Reduce to a simmer, and cook until tender when pierced with the tip of a knife, about 20 minutes. Drain.
While potatoes are cooking, place milk in a small saucepan over medium-high heat just until it comes to a simmer. Reduce heat to low, and keep warm. Place a heatproof bowl over a pan of simmering water. Press hot, drained potatoes through a ricer into bowl. Stir potatoes with a wooden spoon until smooth, about 1 minute.
Stir in butter until completely melted and well incorporated. Slowly pour in hot milk, stirring continuously. Add pepper, nutmeg, and salt; stir to combine. Taste, and adjust for seasoning. Serve immediately.