Allow the croissant pieces to sit out uncovered eight hours to overnight in a large mixing bowl to allow the bread to dry out and stiffen.
Melt butter in a large skillet over medium heat. Add the celery and onion and cook until softened. Stir in garlic in the last 30 seconds.
In a large mixing bowl, whisk together the eggs, stock, heavy cream, sage, rosemary, thyme, poultry seasoning, salt, Dijon mustard and Worcestershire sauce.
Once it becomes one cohesive mixture, stir in the vegetable mixture. Pour the egg mixture over the torn croissant pieces in the large mixing bowl. Stir to coat well.
Spread the croissant stuffing into a greased 9-inch-by-13-inch baking dish. Bake uncovered for 30-35 minutes. Enjoy!