Prep the chicken. If using rotisserie or leftover cooked chicken, remove the skin and chop or shred into bite-size pieces.
Aim for small, even pieces so the dressing coats everything well.
Make the dressing. In a large bowl, whisk together Greek yogurt, Dijon, lemon juice, honey, garlic powder, salt, and pepper. If your yogurt is very thick, add a teaspoon of water or lemon juice to loosen it slightly.
Add the mix-ins. Stir in celery, onion, and herbs. If using apple or grapes, fold those in now along with nuts if you want extra crunch.
Combine with chicken. Add the chicken to the bowl and toss until everything is evenly coated.
Taste and adjust salt, pepper, and lemon. The flavor should be bright, creamy, and balanced.
Chill for best flavor. Cover and refrigerate for at least 20–30 minutes. The flavors meld, and the texture firms up nicely.
Serve your way. Spoon onto toasted sourdough, stuff into whole-grain pitas, wrap in lettuce leaves, top a salad bowl, or enjoy with crackers and raw veggies.