Mix the walnuts, cranberries, mustard, sugar, celery, scallions and some salt and pepper together in a large bowl. Let the flavors meld for 10 minutes.
Add in the mayo and mix until incorporated. Adjust the seasoning if necessary. Add in the chicken. Let the mixture sit in the fridge for at least 1 hour before serving, overnight preferred.
Serve on lettuce leaves and drizzle with balsamic reduction.
This is the perfect opportunity to make use of dry or overcooked chicken breasts.