Boil the potatoes with their skins in plenty of salted water, then rinse and peel them.
Let the potatoes cool down a bit and then press them through a potato press. Add the potato flour, egg yolk, salt and softened butter and knead everything into a dough and season with nutmeg.
Shape the dough into 12 dumplings and place on a floured surface.
Bring plenty of salted water to the boil and let the dumplings stand in it for about 8 minutes, the water should no longer boil but only bubble very gently. Remove the dumplings and let them drain.
While the dumplings are cooking, melt the butter in a little olive oil and add the thyme. Heat everything and fry the dumplings over medium heat for about 10 minutes, turning several times.
A cream sauce with mushrooms or pan-fried food goes very well with this.