Cook the chicken in a large skillet with a drizzle of oil and salt and pepper. Set aside.
In the same skillet, add the butter, onion, carrots, and celery. Cook until softened, about 5-10 minutes.
Sprinkle in the flour and stir until smooth. Cook for about a minute, stirring constantly.
Add chicken broth and milk; cook, stirring constantly until thickened and bubbly, about 10 minutes.
Stir in the cooked chicken, peas, salt, and pepper.
Let this mixture cool before pouring it into pie crusts. This step is very important! It allows the mixture to thicken a bit more.
When you’re ready to eat, pull the entire frozen pot pie out and pop it into a 400-degree oven. Bake it covered with foil for 30 minutes. Then, remove the foil and bake for an additional 30 minutes.
