In a dry skillet over medium heat, add walnuts and toast for 2-3 minutes, tossing every 30 seconds. Remove from heat and allow to cool before chopping and adding to salad.
In a small mixing bowl, whisk together the mayonnaise, yogurt, lemon juice, salt, and pepper.
Toss the chicken, celery, apples, grapes, and walnuts together until evenly combined. Pour the dressing over the chicken mixture and toss to coat.
Cover and refrigerate for at least 30 minutes before serving.
Serve this chicken salad on a bed of lettuce, on a wrap, on crackers, or as a sandwich.
Storage: Waldorf chicken salad will last for 3 days in the fridge. Chicken Waldorf salad does NOT freeze well.Mayonnaise/Yogurt Notes: Feel free to use all mayonnaise or all Greek yogurt for the base of the chicken salad. Be sure to use plain Greek yogurt, but any fat percentage works. Grapes: Red or green grapes can be used or a mixture of both. Apples: For the apples, select a firm sweet or tart apple (based on your preference). Granny Smith, Gala, and Honey Crisp are all great options. Nuts: Omit the nuts if desired.