Boil the potatoes, peel them and mash them together with the parsley with a fork.
Cut the leek into small rings and briefly put in boiling salted water. Then drain the leeks well and add to the potatoes together with the egg yolk, flour and durum wheat semolina and mix everything together until a sticky mass is formed. Season with salt, pepper and nutmeg, shape into small balls and roll the dumplings in flour.
Bring the water to the boil, add the dumplings, bring to the boil again briefly, turn the stove down and simmer on a low level.
If the dumplings swim up, they are ready and can be taken out of the water.