Cut a herring fillet into small cubes. Peel half an apple, remove the core and the stem, cut into thirds lengthways and crossways into thin slices. Also cut the pickles crosswise into thin slices. Cut the onions into rings approx. 4 mm thick. Use 6 large rings for garnishing, use the smaller ones for the cream bed.
Mix the ingredients for the cream bed and season with additional cucumber marinade, pepper and salt. Take the matjes fillets out of the package and let them steep for 2 hours covered in a bed of cream.
In the meantime, wash, peel and round the potatoes. Cook in salted water for 20 minutes. Strain and toss in the melted butter just before serving.
Take the matjes fillets out of the cream bed, mix them and distribute them on the serving plates. Rinse the fillets, pat dry and arrange on the cream bed. Add the potatoes tossed in butter, garnish and serve.