Wash the matjes fillets thoroughly under cold water, pat dry with kitchen paper, halve lengthways and cut diagonally into bite-sized pieces. Peel and quarter the apple, remove the core and cut into small cubes. Quarter the pickles lengthways and cut into small cubes. Peel and quarter the onion, cut into slices and pull apart in strips. Boil the egg hard, quench it, peel it off and later finely dice it with a kitchen helper (bought in the Czech Republic!). Wash the dill, shake dry and cut finely. Put all ingredients (matjes fillet pieces, 150 g Greek yogurt, diced apple, diced cucumber, onion strips, diced egg, 2 tablespoons of cut dill. 1 teaspoon of medium-hot mustard, 2 big pinches of coarse sea salt from the mill and 2 big pinches of colored pepper from the mill) in one Fill the bowl and mix gently. Chill until ready to serve.