Pre-heat the oven to 375˚F.
Brush an 8-inch x 8-inch baking dish with melted butter.
Add the leftover stuffing to the bottom of the pan, squishing it down a little bit. Then smooth a layer of cranberry on top of that.
Layer the mashed potatoes over the cranberry sauce.
In a large mixing bowl, mix up the turkey and gravy, then pour it over the top of the stuffing and cranberry layer.
Scatter the leftover cornbread over the top, then drizzle with the remaining melted butter.
Place the dish on a cookie sheet in the oven and bake until golden brown and bubbly, about 15 minutes.