Cook potatoes in salted water for 30 minutes until fork tender. Peel potatoes and pass through a food mill. In a saucepan, mix potatoes with the butter and stir up on medium heat, then add the cheese. Transfer potato mixture to a bowl, add the egg yolks and stir swiftly; eggs must not cook. Season with salt and pepper to taste. Preheat fan oven to 400ºF/200ºC.

Pipe duchess potatoes into desired shapes using a large open start piping tip. You can spoon them out if you don't have piping tips.

Bake duchess potatoes for 15 minutes until golden brown. Serve immediately. Enjoy!