Toast the almonds: Add sliced almonds to a dry skillet over medium heat. Stir frequently for 3–4 minutes until lightly golden and fragrant.
Transfer to a plate to cool so they stay crisp.
Make the dressing: In a large bowl, whisk together Greek yogurt, mayo, Dijon, honey, apple cider vinegar, garlic powder, onion powder, salt, and black pepper. Taste and adjust—add a pinch more salt, vinegar for tang, or a tiny drizzle of honey if needed.
Prep the mix-ins: Chop the celery and red onion finely. Halve the grapes if using.
Rough chop the parsley.
Add the chicken: Fold the chicken into the dressing until evenly coated. You want it creamy but not soupy. If it looks dry, add a spoonful of yogurt or a splash of vinegar for brightness.
Layer in crunch and freshness: Stir in celery, red onion, parsley, and most of the toasted almonds.
If using grapes, fold them in gently at the end to avoid squishing.
Chill briefly: Cover and refrigerate for 20–30 minutes so the flavors meld. It also firms up the texture, making it perfect for sandwiches or scooping.
Finish and serve: Give it a final taste. Add a crack of pepper and the remaining almonds on top for crunch.
Serve in lettuce cups, on toasted sourdough, wrapped in a whole-grain tortilla, or scooped over mixed greens.