Preheat oven to 375 degrees. If using an acorn squash to cook the stuffing in,microwave the squash for 5-10 minutes. Slice the squash in half, and remove the seeds. Place the squash on the baking sheet and set aside.
To prepare the stuffing, place celery, onion, apple, mushrooms, seasonings, cranberries, and maple syrup in a large nonstick skillet sprayed with cooking spray.
Cover skillet and cook over medium heat, stirring occasionally, until onions become tender (about 5-7 minutes). Remove lid, and continue to sauté until the liquid in the pan is evaporated. Turn off heat and place everything in a large mixing bowl.
Meanwhile, toast the bread in the oven over low broil on a large pan (flipping each piece after about 1-2 minutes, or until each side is golden brown.) Or place each piece of bread in the toaster. Or let it sit out overnight to get stale. Chop bread into small cubes. (If using Cornbread, simply chop cornbread into small cubes, no toasting is necessary).
Mix egg whites, parmesan cheese, bread cubes and bacon in with the onion mixture in the mixing bowl. Stir until well combined.
Put 1 1/2 cup stuffing in each half of the acorn squash (or baking dish if not using squash) and sprinkle pecans over the top of each squash.
Bake for 25-30 minutes, or until bread in stuffing becomes lightly golden brown. Enjoy!