Boil potatoes by peeling and chopping 2 pounds of Russet or Yukon gold potatoes into even chunks and covering them with salted water. Cook for 15-20 minutes until fork-tender.

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

Melt 1/4 cup of unsalted butter and warm 1/4 cup of heavy cream in a small saucepan or microwave.

Mash the drained potatoes until smooth and combine with melted butter, warm cream, grated Parmesan, salt, black pepper, and egg yolks.

Pipe the potato mixture into swirls on the prepared baking sheet.

Brush the tops of the piped potatoes with remaining melted butter and bake for 15-20 minutes until golden brown.

Garnish with chives or parsley and sprinkle with sea salt before serving.