Start by cubing the russet potatoes and placing them in a large pot. Cover the potatoes with cold water, adding a generous pinch of salt. Bring the water to a boil over medium-high heat. Cook the potatoes until fork-tender, about 15-20 minutes. Drain and let steam dry for one minute.

In a mixing bowl, transfer the drained potatoes and mash until smooth. Add butter, egg yolks, heavy cream, salt, pepper, and nutmeg. Mix until creamy and fully combined. Stir in Parmesan cheese if using.

Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper. Scoop the creamy potato mixture into a piping bag fitted with a large star tip.

Pipe the Duchess Potatoes into elegant rosettes or rounds on the prepared baking sheet, leaving space between each.

Bake for 20-25 minutes, watching for the tops to turn golden brown. The aroma will indicate they are almost ready.

Remove from the oven and let them cool slightly before serving warm.