Heat up a pan with half of the butter and toast 1/3 of the bread cubes in it until golden, then add to the remaining bread cubes. Heat the milk and pour over it. Peel and dice the onion and sauté in the remaining butter, but do not let it take any color, then add to the bread cubes. Knead the mixture with the flour and parsley and season with salt and nutmeg. Let it soak for 3/4 hours.
Twist dumplings from the bread mixture with wet hands, the amount makes about 10 pieces, depending on the size.
Let the dumplings simmer in plenty of well-salted boiling water for about 20 minutes.