Wash the trout, dab dry and rub with half of the lemon juice. Wash the herbs and dab dry. Set aside some dill and lemon balm for garnishing. Finely chop the remaining herbs.
Fill the fish with the chopped herbs and tie them into shape with kitchen yarn (dressing). Clean and wash the zucchini, peel and wash the carrots. Cut the vegetables lengthwise into thin slices with a peeler.
Bring 1/4 litre of salted water and remaining lemon juice to the boil. Add bay leaf and trout and simmer covered over low heat for about 15 minutes. Mix quark, milk, yoghurt and mustard and season to taste with salt and pepper.
Briefly fry the vegetables in hot fat. Add some water, pepper and salt and steam for about 3 minutes. Arrange vegetables and trout on a preheated plate and garnish with lemon balm and lemon slices.
Garnish the quark dip with the remaining herbs and add it separately. Add 2 small boiled potatoes per portion.