Boil the Potatoes:
Place the peeled and cubed potatoes into a large pot of cold salted water. Bring to a boil and cook for 15-20 minutes, or until fork-tender. Drain well to remove excess moisture.

Mash Until Silky Smooth:
Pass the potatoes through a ricer or mash until smooth. Avoid lumps to ensure the silky texture of Duchess Potatoes.

Blend in Butter, Cream, and Seasonings:
Stir in the softened butter, warm cream, salt, pepper, and optional nutmeg until fully incorporated and creamy.

Add the Egg Yolks:
Let the potato mixture cool slightly, then stir in the egg yolks one at a time. This helps the swirls hold their shape when baked.

Pipe the Potatoes:
Transfer the mixture into a piping bag fitted with a large star tip. Pipe swirls onto a parchment-lined baking sheet, spacing them apart.

Brush with Egg Wash:
Whisk the remaining egg yolk with milk or cream and lightly brush each swirl with the egg wash to achieve a golden finish.

Bake Until Golden:
Preheat the oven to 400°F (200°C) and bake for 20-25 minutes, or until the tops are golden brown and slightly crisp.

Serve and Impress:
Let the duchess potatoes cool slightly before serving. Pair with roasted meats, holiday mains, or creamy sauces.