Step 1

Preheat your oven to 375 degrees. Line 2 baking sheets with parchment paper.

Step 2

Peel the potatoes and cut into quarters. Place them in a large pot and cover them with water. Bring the water to a boil and cook until the potatoes are soft, about 10-15 minutes. Drain the potatoes.

Step 3

Pass the potatoes through a potato ricer. Alternatively, you can mash them with a potato masher, making them as smooth as possible.

Step 4

Add the butter and let it melt. Mix in the cream, salt, and pepper. Taste and add more salt, if wanted. When the mashed potatoes have cooled slightly, stir in the egg yolks.

Step 5

Transfer the mashed potatoes to a pastry bag fitted with a large star tip. (You'll need to work in batches.) Pipe the potatoes onto the parchment-lined baking sheets into swirls about 3 inches in diameter.

Step 6

Whisk the whole egg with the milk then gently brush it over the duchess potatoes. You don't want to use a lot and you'll likely have leftovers.

Step 7

Bake the potatoes for 20-25 minutes, or until they have started to turn golden along the ridges. Serve with a little minced parsley, chives, or thyme sprinkled over the top.