In a 4-quart Dutch oven cook the potatoes, covered, in enough boiling lightly salted water to cover for 12 minutes or until tender; drain. Remove potatoes from pan.
Add the butter to the hot Dutch oven and let it melt. Add the potatoes to the Dutch oven; mash with a potato masher until smooth. Stir in the sour cream, milk, salt, and pepper. Cook and stir over low heat until heated through. Transfer to a serving dish. If desired, place a dot of butter on top. Makes 8 to 10 servings.
Make-ahead directions: Prepare potatoes through Step 2 but do not heat through. Transfer to a 2-1/2- to 3-quart casserole. Cover and chill for up to 24 hours. Before serving, preheat oven to 325°F Bake, covered, in the preheated oven for 55 to 60 minutes or until heated through.��.
Maple Mashed Sweet Potatoes: Prepare as above. Before serving, drizzle 1/4 cup maple syrup over potatoes and sprinkle with 1/4 cup chopped hazelnuts or almonds, toasted.