In a large mixing bowl, add the shredded chicken, dried cranberries, chopped celery, and finely chopped red onion. Gently toss these ingredients together until evenly distributed.

In a separate medium bowl, whisk together the mayonnaise, Dijon mustard, and the juice of the lemon until smooth and creamy. Season with salt and pepper to taste.

Pour the dressing over the chicken mixture and gently toss until all components are well-coated.

If desired, fold in the chopped walnuts or pecans along with fresh parsley. Gently mix until incorporated.

Taste the salad and adjust seasoning if necessary before chilling it.

Cover the mixing bowl with plastic wrap or transfer the salad to an airtight container and refrigerate for at least 30 minutes.

Once chilled, serve on its own, in a sandwich, or wrapped in lettuce.