Peel and chop the potatoes. Transfer them to a large pot and cover with cold water. Add a pinch of salt and bring to a boil over medium-high heat. Cook for about 15–20 minutes until fork-tender.

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

While the potatoes are cooking, melt the butter in a small bowl in the microwave. Warm the cream in a microwave-safe bowl. Set both aside.

Drain the potatoes thoroughly and return them to the pot over low heat to help evaporate any excess moisture.

Mash the potatoes using a potato ricer or masher until they are smooth and free of lumps.

Add two tablespoons of the melted butter, the warm heavy cream, grated Parmesan (if using), salt, and pepper. Mix well, then stir in the egg yolks until well combined.

Transfer the mashed potato mixture to a piping bag fitted with a large star tip. Pipe the potatoes into small mounds or rosettes onto the baking sheet, spacing them about 1 inch apart.

Brush the potato mounds with the remaining melted butter and bake for 15–20 minutes, or until the Duchess Potatoes are golden brown on the edges and slightly crispy.

Remove from the oven and garnish with fresh chopped chives or parsley. Sprinkle the sea salt over the top, serve immediately, and enjoy.