Peel the potatoes and place in a large pot with and add 1 teaspoon of salt and bring to boil.
Boil them for approximately 20 minutes until soft (exact cooking times will depend on the size of your potatoes). Then drain off the water, and put the pot back onto the stove until all moisture has evaporated.
Mash them with a potato ricer, or potato masher.
Place into a large bowl and mix in the butter. Pour in the potato/corn starch, egg yolks. Lastly, season with a teaspoon of salt and some grated nutmeg (about ¼ teaspoon).
Mix the potato dumpling dough until all the ingredients are combined. (You do not want to mix it too long, as otherwise, the dough becomes too hard and tough.
With your hands, roll the dumplings in about 8 balls. The size is up to you. You can also make smaller ones. (If the dough sticks to your hands, wet your hands with a little water).
In the meantime, bring a large pot of water to boil. Add a teaspoon of salt. Once boiling, reduce the heat. The water should only simmer. Not wildly boil, as otherwise the dumplings might fall apart.
Place the dumplings in the water and leave to sit in the simmering water for about 15-20 minutes. Once the Kartoffelkloss floats to the top it is done.
Remove with a slotted spoon.