Take leftovers out of fridge and allow to come to room temperature.
Preheat the oven to 425 degrees.
Roll out one of the pie crusts and place a pie dish. Add in the turkey, then the pan drippings or gravy, then the cranberry sauce, then the mashed potatoes, and finally a layer of crumbled cornbread or chopped stuffing.
Cover with the top crust and crimp the edges to seal. Cut 2 slits in the top crust--these will be steam vents.
In a small bowl, beat the egg with the water. Use a pastry brush to lightly brush all exposed pastry. This will make it nice and shiny!
Place the pie on a sheet pan and bake for 35 minutes until golden brown.