01 - In a large bowl, mix the cooked chicken, celery, red onion, grapes, and nuts if using.
02 - In a small bowl, whisk together mayonnaise, Greek yogurt, Dijon mustard, lemon juice, salt, and black pepper until smooth.
03 - Pour the dressing over the chicken mixture and gently toss until evenly coated.
04 - Fold in the chopped fresh parsley carefully.
05 - Cover and refrigerate for at least 15 minutes to allow flavors to meld.
06 - Serve scoops of the salad on a bed of lettuce, alongside crackers, or inside a sandwich.