Same way my mom made it.
Boil chicken in chicken broth with celery, onion and poultry seasoning. You can use a whole chicken, chicken breast or thighs or whatever pieces you want really. Debone and remove skin if needed and cut up meat.
Melt a stick of butter in a skillet, add flour to make a roux. Stir and cook for a couple of minutes. Add broth you boiled the chicken in to make a gravy. Add a bag of peas and carrots and heat them through. Add cutup or shredded chicken meat. Pour into a casserole dish and top with a pie crust. Bake until bubbly and pie crust is brown.
You can put a second crust on the bottom if you like. Or you can use puff pastry. Some like to add melted butter to the top of the crust. I use pre made pie crust but you can make your own. You can also top with uncooked frozen or homemade biscuits and bake until they are cooked through.