Peel the shallots and cut into rings. Quarter the apple, peel it, cut into wedges and cut the wedges into small pieces, then add to the shallots. Cut the gherkins into small slices and add. Add the herring fillets to the other ingredients and cover everything with the cream. Add a dash of white wine vinegar and the dill tips. Do not add salt, the matjes are salty enough. Cover and refrigerate for at least 12 hours.
After the resting time, add the crème fraîche. If the marinade is too acidic, add sugar to taste.
Cook the potatoes with their skin on but without salt for about 20-25 minutes.
Cut the potatoes lengthways and place a herring with sauce in each. Arrange and serve.