Wash the lemon, rub dry and grate some of the peel thinly. Halve the lemon, squeeze the juice. Mix sour cream, mayonnaise, lemon peel and juice. Season with salt, pepper and sugar
Clean, wash and drain the salads. Pluck leaves a little smaller. Peel and wash carrot and celery. First grate the carrot and then the celery into fine sticks. Mix both immediately into the sauce. Arrange on salad leaves. Wash the parsley and garnish the salad