Pour egg mixture over croissants; press croissant pieces into egg mixture to moisten completely. Cover tightly with foil and refrigerate for at least 8 hours but no longer than 24 hours.Preheat oven to 325 degrees. Bake, covered, for 35 minutes. Uncover and bake 25 to 30 minutes longer or until knife inserted in center comes out clean. Let stand 10 minutes before serving.