Start by peeling and chopping 2 pounds of Russet or Yukon Gold potatoes into even chunks. Place them in a large pot of salted water over medium heat. Bring the water to a boil and cook the potatoes until they are fork-tender, about 15–20 minutes. Once done, drain them well, ensuring there’s no excess moisture.

While the potatoes cool slightly, preheat your oven to 425°F (220°C). Prepare a baking sheet by lining it with parchment paper.

In a small saucepan over low heat, melt 3 tablespoons of unsalted butter, then add 1/4 cup of heavy cream, warming it just until hot but not boiling. Remove the mixture from the heat and set aside to cool slightly.

Mash the drained potatoes in a large bowl until smooth and free of lumps. Gradually mix in the melted butter and warm cream, followed by 1/4 cup of grated Parmesan cheese, 1 teaspoon of salt, and 1/2 teaspoon of black pepper. Add in 3 large egg yolks until well combined.

Transfer the fluffy potato mixture into a piping bag fitted with a star tip. Pipe small mounds of the mixture onto the prepared baking sheet, leaving space between each swirl.

Brush the tops of the piped potato swirls with the remaining melted butter. Bake for 15-20 minutes, or until the tops are crisp and golden brown.

Once baked, remove the Duchess Potatoes from the oven. Garnish them with freshly chopped chives or parsley and sprinkle a little sea salt on top.