Cook potatoes with their skins in a little boiling water with caraway seeds for about 20 minutes.
Dice beetroot and cucumber, peel and core the apple. Peel the onion. Roll both dice. Mix with the salad cream and spices, season to taste. Pick up the trout fillets with two forks and fold in. Finely chop the dill.
Peel the potatoes. Fry in hot butter until golden brown, then top with the dill.