In a large mixing bowl, combine mayonnaise, Greek yogurt, and lemon juice.
Add green onions, brown sugar, fresh dill, kosher salt, garlic powder, and black pepper. Stir until smooth and well combined.
Fold in the chopped chicken, celery, grapes, and cashews.
Mix thoroughly until everything is evenly coated with the dressing.
Cover and refrigerate for at least 15 minutes to allow the flavors to blend.
Taste and adjust seasoning with additional dill, salt, or pepper if desired.
To serve this Chicken Salad Croissant Recipe, spoon the chicken salad onto the bottom half of each croissant.
Add lettuce and tomato slices if desired.
Place the top half of the croissant over the filling and serve immediately.