In a bowl, stir together mayonnaise, apples, celery, 1/2 cup walnuts, cranberries, parsley, salt and pepper.
Tear chicken into chunks, discarding skin and bones. Stir into apple mixture. (Salad may be KITCHEN TIPS prepared up to 6 hours ahead.)
To serve, line a bowl with watercress or arrange on a platter and top with chicken salad. Sprinkle remaining 1/2 cup walnuts over chicken.