Prepare your chosen pie crust recipe through step 5, ensuring it chills for at least 2 hours; making it the night before is recommended as you'll use both crusts.

In a large pot, combine cubed chicken, sliced carrots, and celery, then cover with water and bring to a boil for 10 minutes before draining and setting aside.

In a large skillet, cook butter, onions, and minced garlic over medium heat until onions are translucent and butter lightly browns. Whisk in flour, seasonings, chicken broth, and half-and-half, cooking until smooth and simmering for about 10 minutes until the gravy is very thick, adjusting seasonings to taste.

Preheat oven to 425°F (218°C).

Roll out one chilled dough disc into a 12-inch circle on a floured surface, then carefully place it into a 9-inch pie dish, tucking it in smoothly and trimming any excess overhang.

Spoon the cooked chicken and vegetable mixture into the crust, scatter frozen peas on top, and evenly pour/spread the thick gravy over everything.

Roll out the second dough disc, cover the pie, trim excess dough, and crimp the edges with a fork to seal, then make a few small slits in the top crust and brush with egg wash.

Bake for 32–38 minutes until the crust is golden brown, making sure to cover the edges with aluminum foil after 20 minutes to prevent over-browning.

Remove the pot pie from the oven and cool for at least 10 minutes before serving, noting that leftovers are excellent and keep well in the refrigerator for up to 5 days.