Cook the Potatoes

1. Boil the Potatoes: Peel the Yukon Gold potatoes and cut them into chunks. Place them in a large pot of salted water and bring to a boil. Cook for 15-20 minutes, or until the potatoes are fork-tender.
2. Drain and Mash: Once the potatoes are cooked, drain them well and return them to the pot. Mash the potatoes until smooth and creamy.

Make the Potato Mixture

1. Add Butter and Milk: Stir in the butter, milk, and nutmeg. If you’re using garlic powder and Parmesan cheese, add them at this point as well. Season with salt and pepper to taste, and continue to stir until everything is fully combined and the mixture is smooth and fluffy.

Pipe the Potatoes

1. Preheat the Oven: Preheat your oven to 400°F (200°C).
2. Prepare the Piping Bag: Transfer the mashed potato mixture into a piping bag fitted with a large star tip (or use a plastic sandwich bag with the tip cut off). If you don’t have a piping bag, you can also spoon the mixture onto the baking sheet and shape them with a spoon.
3. Pipe onto Baking Sheet: On a greased baking sheet, pipe the potatoes into rosettes or any shape you like, leaving a little space between each one.

Bake the Duchess Potatoes

1. Brush with Egg Yolk: In a small bowl, whisk the egg yolk with a teaspoon of water. Gently brush the top of each piped potato with the egg yolk to help them turn golden and crisp up in the oven.
2. Bake: Place the baking sheet in the oven and bake for 20-25 minutes, or until the potatoes are golden brown and slightly crispy on the edges.

Serve

1. Garnish: Once they’re baked, garnish with a sprinkle of freshly chopped parsley for a pop of color and fresh flavor. Serve hot!