I’m not sure how this tradition got started, but it’s a great way to use up some of the leftovers that nobody really wants to snack on. I also don’t really have a “recipe” in the traditional sense, as I use whatever leftovers are available, and that changes from year to year. The size of the pie and the number it will serve depends on how many leftovers are available. But here’s the basics:

leftover turkey, cut into cubes
leftover pearl onions (or a small onion, chopped)
leftover relish-dish celery, chopped
leftover veggies, whatever is available
leftover gravy
leftover mashed potatoes

Combine first four ingredients in a casserole dish. Add a enough water to the gravy to make a nice sauce for the pie and pour over other ingredients in the dish. Top with leftover mashed potatoes. Sprinkle potatoes with shredded cheddar cheese. Bake at 375 - 400 until pie is hot and bubbly and cheese is melted.