Preheat oven to 425. Line a 9" pie dish with the first pie crust.
Heat a large stockpot over medium heat. Add the butter, carrots, and celery. Cook for 5 minutes stirring occasionally.
Add the cornstarch and chicken stock into a bowl and stir to combine to create a slurry. Pour into the stockpot.
Add the remaining ingredients into the stock pot and stir until it thickens.
Pour the chicken pot pie mixture into the prepared pie crust.
Take the second pie crust and drape over the top. Use a fork or your fingers to crimp the edges shut. With a sharp knife, cut a couple slits in the top for the steam to escape.
You can brush the top with an egg wash and sprinkle with salt if desired.
Bake for 30-35 minutes or until the top is golden brown and the filling is bubbly.
Allow to cool for 10 minutes before slicing and serving.