Soak the herring fillets for half an hour. Prepare a marinade from sugar and vinegar, cool. Add onion rings, gherkin slices and unpeeled apple slices. Add whipped cream, pepper, yogurt, salt and vinegar-sugar marinade and stir well. Pour in the drained halved herring fillets.
Leave the herring pot in a cool place for 2 days until ready to use.
Tip: Use creamy natural yogurt for an even finer result!