For the Pommes Duchesse, steam the peeled potatoes, strain them while still hot and stir them together with butter, egg yolks, salt and nutmeg briefly on the stove in a saucepan until smooth. The less you stir, the better the mixture will be.
Fill the mixture into a piping bag with a star-shaped nozzle and pipe onto a greased baking tray. Brush with egg and bake briefly in the oven.
Remove the finished Pommes Duchesse from the oven and enjoy hot.