01 - In a large bowl, mix the cooked chicken, celery, red onion, grapes, and parsley until evenly distributed.
02 - Whisk together mayonnaise, Greek yogurt, Dijon mustard, lemon juice, salt, and black pepper in a separate small bowl until smooth.
03 - Pour the dressing over the chicken mixture and toss thoroughly to coat all ingredients.
04 - Fold in the chopped walnuts or almonds gently, if using.
05 - Taste the salad and adjust seasoning if necessary. Refrigerate for at least 30 minutes to enhance flavors.
06 - Present the salad on a bed of lettuce, in sandwiches, or accompanied by crackers.