Boil the eggs in boiling water for about 10 minutes until hard, drain, rinse cold and peel. Drain mustard gherkins and collect the gherkin water. Mix mustard, yoghurt, sour cream, 4 tablespoons cucumber water and apple juice.
Season to taste with salt, pepper and sugar. Peel onions and cut into rings. Cut gherkins into slices. Wash and quarter apples and cut out the cores. Cut apple quarters into fine slices.
Cut the herring into pieces. Wash the dill, dab dry, cut finely and stir into the yoghurt cream. Cut the eggs into slices. Carefully mix onions, gherkins, gherkins, apple slices, Bismarck herring and eggs.
Leave the salad in a cool place for about 1 hour. Season again with salt, pepper and sugar. Serve garnished with dill pennants and a slice of lemon if desired.