1. Slice the apple in half, core it and dice the apple up into bite-size chunks. Rinse the celery stalks and slice them up finely. Add the celery and the diced apple to a large mixing bowl.
2. Stir well. Rinse the grapes and slice them in half. Add the grapes to the mixing bowl. Drizzle with half of the lime juice.
3. Stir well. Finely chop the fresh parsley up and add it to the bowl together with the mayonnaise, the shredded cooked chicken and the chopped walnuts.
4. Stir well again. Check the seasoning and add extra pepper, salt, lime juice or mayonnaise to taste if necessary.
5. Stir one last time. Divide the lettuce over plates and top with the chicken waldorf salad. Serve at room temperature.