Drain the herring, remove the fins if necessary, cut into small pieces and place them in a large bowl. Dice the cucumbers very small and add to the herring. Wash the apple, peel it, dice it very small and add it to the bowl with the herring. Peel the onion, cut into thin slices, quarter the slices, cut into individual pieces and add to the bowl. Add peppercorns, allspice grains and bay leaf.
Mix the sour cream with a little milk until creamy. Add the cream to the bowl with the other ingredients. Mix all ingredients well. Add a little sugar or sweetener to taste.
Cover and let steep in the refrigerator for about 12 hours. Before serving, season again with sugar or sweetener and stir vigorously.
Boiled potatoes go best with this. The marinated herring is served cold with hot potatoes.