Boil the potatoes in salted water and let them cool.
Press the cooled potatoes through a ricer until smooth.
Divide the mashed potatoes into four parts, remove one, and fill the empty space with potato starch.
Add the egg yolk and knead into a smooth dough.
Form small dumplings and make a small indentation in the center of each.
Cook the dumplings in lightly boiling salted water with a bit of oil.
Remove two minutes after they float to the surface. Serve with sauce or meat.