In a large skillet, saute celery, onion, and apples in butter until tender.
Remove from the heat and set aside.
In a large bowl, combine the stuffing cubes, broth, and celery mixture
Transfer to a baking dish (9" x 13") that has been sprayed with non-stick cooking spray, spread stuffing mixture around in the baking dish.
In another large bowl, combine the turkey, soup, garlic powder and ¼ cup sour cream.
Spoon turkey mixture over stuffing mixture.
Spread mashed potatoes over turkey mixture.
Season with salt and pepper. Sprinkle with cheese.
Bake uncovered at 350℉ for 35-40 minutes or until heated through.
Notes
This recipe allows for more customizations. Feel free to use whatever Thanksgiving leftovers you have, and continue layering. Popular layers include cornbread stuffing, sweet potatoes, corn casserole, macaroni and cheese, and green beans. If you have french fried onions, you can top the casserole with them.