Place the potato chunks in a large pot and cover them with cold water. Add a pinch of salt.

Bring the pot to a boil over medium-high heat and cook until the potatoes are tender, about 15-20 minutes.

Drain the potatoes well and return them to the hot pot. Let them sit for a minute or two to remove excess moisture.

Add half of the softened butter to the hot potatoes. Mash until smooth and lump-free (a potato ricer or masher works well).

Stir in the heavy cream, egg yolks, salt, black pepper, and nutmeg (if using). Continue mashing until the mixture is light, fluffy, and well combined.

Preheat the oven to 425°F (220°C) and line a baking sheet with parchment paper.

Transfer the potato mixture to a piping bag fitted with a large star tip.

Pipe the mashed potatoes onto the prepared baking sheet into decorative swirls or mounds, leaving some space between each.

Brush the tops of each potato mound with the remaining butter.

Sprinkle a little grated Parmesan cheese on top of each mound if desired.

Bake in the preheated oven for 15-20 minutes, or until the potatoes are golden brown on the edges and lightly crisp on top.

Serve hot as a side dish. Enjoy the rich, buttery flavor of these elegant Duchess Potatoes!