In fry pan add a small amount of oil. saute onion, celery, potato and carrots. Depending on how much turkey you have leftover and how many pies you are making will depend on how many carrots and potato's you will need. I usually use about a cup for each large pot that I make which makes about 2 pies.
Cover with just enough water to barely cover vegetables. Cook until tender. You do not need to drain the water.
Add the gravy. I use the leftover gravy from our dinner but you can use store bought. Usually 2 cups is enough but, again it depends on how much you are making. Add the peas at this point as well. Put the crust on top and cut holes in the top. You can also use biscuits as a topper. Place in the oven for 30-40 minutes at 450 degrees.