There are a million recipes for this simple side dish. Why? Because we can't get enough of them. Because at Thanksgiving, mashed potatoes, gravy and cranberry sauce are three "sauces" for the turkey. Leftover mashed potatoes warmed in the oven and slid into the layers of a turkey sandwich are sublime. I love the salt of the Parmesan in here. I also love the last-minute "fluff" that the whipped cream brings to the party.
Cook the potatoes: In a large pot, add the potatoes and cover amply with cold water. Bring the water up to a boil and reduce the heat so it simmers. Add a generous pinch of salt to the water and allow the potatoes to cook until tender when pierced with the tip of a knife, 20 to 25 minutes. Drain the potatoes in a colander and, while still hot, put them through a food mill.
Mash the potatoes: Return the empty pot to the heat and add the milk. Bring the milk to a simmer and gingerly add the potatoes back into the pot. Season with salt and pepper and gently mix in the butter and sour cream. Do not over mix – over mixing makes gummy potatoes. Taste for seasoning. Remove from the heat.
Finish the potatoes: When ready to serve, use a whisk (or an electric mixer fitted with the whisk attachment) to whip the heavy cream in a medium bowl until fairly firm. With a rubber spatula, gently fold the whipped cream and the Parmesan into the mashed potatoes. Taste for seasoning. Serve immediately.