Prepare the chicken:
Use shredded or cubed cooked chicken (rotisserie chicken works great). Place it in a large mixing bowl.
Add the mix-ins:
Add the halved grapes, chopped celery, and red onion (if using) to the bowl. For added crunch, stir in almonds or walnuts.
Make the dressing:
In a small bowl, whisk together mayonnaise, Greek yogurt, Dijon mustard, lemon juice, salt, and pepper until smooth.
Combine the salad:
Pour the dressing over the chicken mixture. Gently toss until everything is evenly coated.
Chill (optional):
For the best flavor, refrigerate the salad for at least 30 minutes before serving.
Serve:
Serve on a bed of lettuce, stuffed into croissants, or sandwiched between slices of bread. Enjoy!