Wash the potatoes, cook for about 20 minutes until they are cooked through. Drain, let cool a little and peel. Wash the beetroot thoroughly, cook with the skin on for about 1 hour and then peel it. Peel the apples and remove the core. Dice the potatoes, beetroot, apples and pickles. Debone herring fillets and also dice. Peel and dice the onion, mix with salt, mustard, sugar and vinegar. Stir in the cream, mix everything together. It is best to let the salad steep overnight. Serve with sliced eggs and parsley.