Peel and cube the Greenstar apples. Dice the chicken breast, cheese und blanched celery and roughly chop the walnuts. Thoroughly mix all ingredients except the lettuce.
Prepare the dressing by beating together the mayonnaise, sour cream, yoghurt, mustard and some salt and pepper to taste. Stir the sauce into the salad.
Arrange the iceberg lettuce on a plate and spoon the salad on top.