Cook sausage and bacon separately in a large skillet until cooked & crisp. Reserve 1 tbsp of bacon grease in the pan and add the onions, celery, and mushrooms then cook, stirring often, until soft and tender, about 5 minutes.
Preheat the oven to 350 degrees. Coat a large baking dish with cooking spray.
Combine the seasoning packet (included with the stuffing mix) with the broth and butter in a large saucepan over medium heat. Bring to a low boil for 3-5 minutes.
Place croutons in a large bowl along with onion, celery, and mushroom mixture along with the bacon, sausage, and chestnuts.
Pour liquid over the mixture and toss lightly until evenly coated.
Spoon the filling into the baking dish. Cover and bake for 40 minutes.
Remove the cover and bake for an additional 5-7 minutes to crisp the top. Fluff and serve. Enjoy.