Creating exquisite Duchess Potatoes can be done easily by following these simple steps:

1. Preheat Oven: Preheat your oven to 400°F (200°C).
2. Prepare Potatoes: Peel and cut the Yukon Gold potatoes into quarters. Place them in a large pot of cold, salted water.
3. Cook Potatoes: Bring the pot to a boil and cook until the potatoes are fork-tender (about 15–20 minutes).
4. Drain and Dry: Drain the potatoes and let them steam dry for a few minutes in the pot to remove excess moisture.
5. Mash Potatoes: Use a potato ricer or a masher to mash the potatoes until smooth and fluffy.
6. Mix in Ingredients: Add butter, heavy cream, egg yolks, salt, pepper, and nutmeg (if using). Mix until well combined and creamy.
7. Pipe the Potatoes: Transfer the potato mixture into a piping bag fitted with a star tip. Pipe small spirals or mounds onto a parchment-lined baking sheet.
8. Add Egg Wash: If desired, beat the additional egg and brush it over the tops of the potato mounds for a golden finish.
9. Bake: Place the baking sheet in the preheated oven and bake for 20–25 minutes or until the tops are golden brown and crispy.
10. Garnish and Serve: Remove from the oven, garnish with fresh parsley, and serve hot.

Follow these straightforward instructions to impress your guests with beautiful Duchess Potatoes that are as delicious as they are visually stunning.