Step 1: Boil the Potatoes

1. Place the peeled and cubed potatoes in a large pot and cover them with cold water. Add a generous pinch of salt.
2. Bring the water to a boil over medium-high heat, then reduce the heat and simmer for 15–20 minutes, or until the potatoes are fork-tender.

Step 2: Mash the Potatoes

1. Drain the cooked potatoes and return them to the pot. Allow them to sit for 1–2 minutes to let any remaining moisture evaporate.
2. Use a potato masher or a ricer to mash the potatoes until smooth. Avoid overmixing to prevent the potatoes from becoming gummy.

Step 3: Add the Cream and Butter

1. Stir in the softened butter and warmed heavy cream until fully incorporated.
2. Season the potatoes with garlic powder (if using), nutmeg, salt, and black pepper to taste.

Step 4: Add the Egg Yolks

1. Gently fold in the egg yolks one at a time, mixing until the potatoes are smooth and creamy. The yolks will help the potatoes hold their shape during baking.

Step 5: Pipe the Potatoes

1. Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
2. Transfer the mashed potato mixture to a piping bag fitted with a large star tip.
3. Pipe the potatoes into swirls on the prepared baking sheet, leaving a bit of space between each for even baking.

Step 6: Brush with Egg Wash

1. Lightly brush each potato swirl with the egg wash to enhance the golden color and crispiness during baking.

Step 7: Bake

1. Bake the Duchess Potatoes in the preheated oven for 20–25 minutes, or until the edges are golden brown and slightly crisp.

Step 8: Garnish and Serve

1. Remove the potatoes from the oven and let them cool for a few minutes. Garnish with fresh parsley or chives if desired, and serve warm.