Peel and cut the potatoes into thin slices.
Peel and cut the fish into portions. Salt to taste.
Cut the onion into half rings.
Put butter on the bottom of the cauldron, then fish, bay leaf, onion and potatoes. Sprinkle a little pepper and salt on each layer.
Pour all the sour cream and simmer over low heat until the potatoes are ready, about 30-40 minutes.
Sprinkle with chopped herbs before serving.