Start by peeling and chopping the Russet or Yukon Gold potatoes into evenly sized pieces. Place them in a large pot, cover with cold salted water, and bring to a boil over medium-high heat. Cook for about 15-20 minutes until fork-tender, then drain thoroughly.

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

In a small saucepan, melt 2 tablespoons of unsalted butter over low heat. Add the heavy cream and warm gently until just heated through, then set aside.

Return the drained potatoes to the pot and mash until smooth. Incorporate the butter and cream mixture, followed by Parmesan, salt, black pepper, and egg yolks. Mix until well combined.

Transfer the creamy potato mixture into a piping bag fitted with a star tip. Pipe small mounds of the mixture onto the prepared baking sheet.

Brush the piped mounds with the remaining melted butter. Bake for 15-20 minutes or until golden brown and crispy.

Remove from the oven, garnish with fresh chives or parsley, and serve immediately.