Clean and wash the salad, pluck into bite-sized pieces and drain. Wash and cut off 2 boxes of cress and mix with the crème fraîche. Puree finely with the cutting stick of the hand mixer. Whip the cream until semi-stiff and fold into the cress cream. Season the cress foam with horseradish and salt. Cut trout fillets into large pieces.
Arrange trout fillets, salmon and shrimps with the salad on plates. Spread the cress foam on the plates. Cut off the rest of the cress and sprinkle the cress foam over it. Mix vinegar with salt and pepper. Whip the oil under it and pour over the salad. Garnish plates with lemon slices and dill