This is the Thanksgiving equivalent to the kitchen sink burrito. You can use a bunch of your leftovers, and it really is easy. Everything should be cooked, and unfrozen.
preheat oven to 375
cut up turkey - white or dark meat
cooked veggies (peas, carrots, corn, broccoli, green beans, creamed onions..... almost anything will work except squash)
3 Tablespoons butter
1/2 cup flour (does not need to be wheat, and you can sub cornstarch - you will need MUCH LESS cornstarch)
1 cup milk (does not need to be dairy - but should be UNSWEETENED. I have used Coconut Dream and Soy Dream)
1 cup turkey broth
pie crust (alternatively, you can make without crust, and serve as a stew)
put turkey - however much you have - in the bottom of an oven-safe pan. I bake this in a dutch oven, but it can be baked in any sort of pan, whatever size you need - or have. Add veggies.
In a sauce pan, melt butter. Stir in flour until it is all coated and forms a paste. Add milk, slowly, while whisking, over medium-high heat. You want it to be simmering (bubbling) but not at a rolling crazy high boil. Once the sauce has thickened - and is almost paste-like, add the broth slowly, continuing to stir with the whisk. You want this sauce to end up the consistency of very heavy cream. Once you have it where you want it, pour over the turkey and veggies, put the pie crust on top (or skip the crust, but maybe cover with a lid or some foil) and stick it in the oven for about 45 minutes.