Start by peeling and chopping the Russet or Yukon Gold potatoes into uniform pieces. Place them in a large pot and cover with cold, salted water. Bring to a boil over medium-high heat and cook for about 15-20 minutes, or until fork-tender. Once done, drain the potatoes well and return them to the pot to allow any excess steam to escape.

As your potatoes cool slightly, preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper to prevent sticking and ensure an even bake.

While the oven preheats, melt 2 tablespoons of the unsalted butter in a small saucepan and warm the heavy cream gently. Mash the drained potatoes until smooth and fluffy, then incorporate the melted butter, warm cream, grated Parmesan, salt, black pepper, and egg yolks.

Transfer the fluffy potato mixture into a piping bag fitted with a star tip. On the prepared baking sheet, carefully pipe mounds of the potato mixture, making lovely rosettes.

Before baking, brush each piped mound generously with the remaining melted butter. Place in the oven and bake for 15-20 minutes until golden-brown and crispy.

Once done, remove the Duchess Potatoes from the oven, let cool for a minute, garnish with freshly chopped chives or parsley, and serve immediately.