01 - In a large bowl, combine the chicken, Caesar dressing, Parmesan cheese, lemon juice, Dijon mustard, celery, and red onion. Mix thoroughly until all ingredients are evenly coated. Season with salt and pepper to taste.
02 - Slice each croissant horizontally without cutting completely through, creating a pocket that can hold the filling.
03 - Line the bottom half of each croissant with a layer of chopped romaine lettuce.
04 - Spoon a generous portion of the chicken Caesar salad mixture onto the lettuce layer in each croissant.
05 - Top with extra Parmesan shavings if desired. Gently close the croissants and serve immediately.