Begin by peeling the Russet or Yukon Gold potatoes and cutting them into uniform chunks. Add the potatoes to a large pot of salted water and bring to a boil over medium-high heat. Cook for 15–20 minutes until the potatoes are fork-tender. Drain them well, then let sit for a couple of minutes to ensure all the moisture evaporates.

While the potatoes are cooling, preheat your oven to 425°F (220°C) and line a baking sheet with parchment paper.

In a small saucepan, melt 2 tablespoons of butter over low heat. Meanwhile, pour the heavy cream into a microwave-safe container and warm it in the microwave for about 30 seconds.

Once the potatoes are dry, transfer them into a large mixing bowl and mash them until completely smooth and creamy. Stir in the melted butter, warm cream, grated Parmesan cheese, salt, black pepper, and egg yolks.

Transfer the creamy potato mixture into a piping bag fitted with a star tip. Pipe small mounds onto the prepared baking sheet, making sure to leave enough space in between for them to expand as they bake.

Take the remaining melted butter and gently brush it over the tops of the piped potato mounds. Place the baking sheet in the preheated oven and bake for about 15–20 minutes, or until the tops are beautifully golden brown and crispy.

Once out of the oven, let the Duchess Potatoes cool for a minute. Garnish with freshly chopped chives or parsley, and sprinkle with a pinch of sea salt.