Put 2 pounds whole unpeeled russet or Yukon gold potatoes in a large saucepan and cover with cold water; add 2 tablespoons kosher salt. Bring to a simmer (do not boil) and cook until the potatoes are tender, about 45 minutes.
Drain the potatoes, then peel and return to the pan; add 1 cup hot milk and 1/2 to 1 stick room-temperature unsalted butter. Mash with a potato masher or fork. Season with salt and pepper.
Photograph by Levi Brown