Preheat your oven to 425 degrees Fahrenheit.
Place one pie crust in the bottom of a 9-inch pie dish.
In a large skillet, melt the butter over medium heat. Add the onion and sauté until soft and translucent.
Add the flour to the skillet and stir until combined. Cook for 1-2 minutes until the mixture turns slightly brown.
Gradually whisk in the chicken broth and milk. Stir constantly until the mixture thickens.
Add the shredded chicken, frozen peas, frozen carrots, salt, black pepper, and garlic powder. Stir to combine.
Pour the chicken mixture into the pie crust.
Roll out the second pie crust and place it on top of the chicken mixture. Crimp the edges to seal.
Cut a few slits in the top of the pie crust to allow steam to escape.
Bake for 30-35 minutes or until the crust is golden brown and the filling is bubbly.
Let the pie cool for a few minutes before serving.