Step 1

In a large pot, bring 4 quarts of water and 2 tablespoons salt to a boil.  Meanwhile, peel the potatoes and cut them into 1½-inch cubes.  Add them to the boiling water and bring the water back to a boil.  Lower the heat and simmer uncovered for 10 to 15 minutes, until the potatoes fall apart easily when pierced with a fork.

Step 5

Meanwhile, heat the whole milk and butter in a small saucepan, making sure it doesn’t boil.  Set aside until the potatoes are done.

Step 35

As soon as the potatoes are tender, drain them in a colander.  Place a food mill fitted with a small disk or blade over a heatproof bowl.  Pass the potatoes through the food mill, turning the handle back and forth.  As soon as the potatoes are mashed, stir in the hot milk-and-butter mixture with a rubber spatula.  Add enough buttermilk to make the potatoes creamy.  Add 2 teaspoons of salt and the pepper, or more to taste, and serve hot.  To keep the potatoes warm, place the bowl over a pan of simmering water for up to 30 minutes.  You can add a little extra hot milk to keep them creamy.