For the sour cream dumplings, sauté the onion in butter until translucent, pour in hot milk and bring to a boil. Empty over the bread cubes and season to taste.
Stir in sour cream and eggs and let rest for about 15 minutes. Form into 1-2 rolls and twist into plastic wrap, let stand in boiling salted water for about 25 minutes.
Unwrap the sour cream dumplings from the foil, cut into slices and serve as a side dish.