Peel the potatoes, cut them into 1-inch cubes and place them in a large pot of boiling salted water. Simmer uncovered for 10 to 12 minutes, until the potatoes are tender. Drain the potatoes in a colander and then return them to the pot.
Meanwhile, heat the milk and butter in a small saucepan until the butter is melted.
Put the potatoes into the bowl of an electric mixer fitted with a paddle attachment and mix them for a few seconds on low speed, to break them up. At low speed, slowly add the hot milk/butter mixture to make the potatoes very creamy. Add the sour cream, 2 teaspoons of salt and the pepper and mix to combine. Serve hot.
Truffle Butter Mashed Potatoes: Add 3 tablespoons room temperature white truffle butter to the Classic Mashed Potatoes and combine.
Parmesan Mashed Potatoes: Add 1/2 cup freshly grated Parmesan to the Classic Mashed Potatoes and combine.
Garlic Mashed Potatoes: Place 1/2 cup garlic cloves and 1/2 cup olive oil in a small saucepan, bring to a boil, lower the heat and simmer for 20 minutes. Allow to cool for 20 minutes and then add the garlic cloves and 3 tablespoons of the oil to the Classic Mashed Potatoes and combine.