Duchess potatoes look fancy, but they are surprisingly easy to make. Just stir egg yolks, butter, cream, plenty of salt and pepper, and a dash of nutmeg into mashed potatoes, then pile the mixture into a pastry bag and pipe it onto a baking sheet in any shape you like. Sprinkle with a little shredded cheese, bake, and you’ll have an elegant potato side dish for your Thanksgiving meal, Christmas table, or even a weeknight dinner party.
6 tablespoons unsalted butter (3/4 stick), cut into 8 pieces, at room temperature
1/4 cup heavy cream, at room temperature
1 teaspoonkosher salt, plus more as needed
1/4 teaspoon freshly ground black pepper
1/8 teaspoon freshly grated nutmeg
1/2 cup finely shredded Swiss cheese, grated on the small holes of a box grater (about 1 ounce)
Heat the oven to 400°F and arrange the racks to divide the oven into thirds. Line 2 baking sheets with parchment paper and set aside.
Wash and peel the potatoes, cut them into 1-1/2-inch chunks, and place in a large saucepan. Cover with 1 1/2 to 2 inches of cold water and salt generously. Bring the potatoes to a boil over high heat. Reduce the heat to medium low and simmer until the potatoes can be easily pierced with a knife, about 15 minutes.
Drain in a colander. Return the potatoes to the pot and mash with a potato masher until very smooth. (Alternatively, use a potato ricer.)
While the potatoes are still warm, mix in the egg yolks 1 at a time using a wooden spoon or rubber spatula, making sure each yolk is completely incorporated before adding the next. Add the butter, cream, measured salt, pepper, and nutmeg and stir until the butter has melted and the mixture is smooth.
Transfer to a large piping bag fitted with a 1/2-inch star piping tip and pipe 12 round mounds (2 1/2 inches wide by 2 inches tall) onto each prepared baking sheet, spacing them about 2 inches apart. Sprinkle with the cheese.
Place both sheets in the oven and bake for 15 minutes. Rotate the pans top to bottom and front to back and continue baking until the tops of the potatoes are light golden brown, about 10 minutes more.