I always make my pot pie from leftover chicken dinner, cut up chicken/turkey, saute onions, carrots, celery, potatoes then steam to finish, add to chicken, add leftover gravy, cool completly then turn into a pieshell and bake until crust is done.
I find this method works much better when your gravy was made using flour as opposed to corn starch.
Always add herb d province to the pot. or rosmary, tyme and sage.