In a medium bowl, stir together the mayonnaise, Dijon mustard, honey, garlic powder, and dried dill until smooth. Gently fold in the shredded chicken and halved grapes. Season with salt and pepper to taste.
Cover and chill for 30 minutes so the flavors can come together.
Spoon the chicken salad into sliced mini croissants and, if desired, finish with a small sprig of fresh dill, if desired.