Preheat your oven to 425°F (220°C).
In a saucepan, melt butter over medium heat.
Stir in flour, onion powder, and garlic powder to create a roux.
Gradually whisk in chicken broth and milk until smooth.
Cook until the mixture thickens, stirring constantly.
Add shredded chicken and frozen vegetables to the sauce, mixing well.
Roll out one pie crust into a pie dish.
Pour the chicken mixture into the crust.
Cover with the second pie crust, sealing the edges.
Cut slits in the top crust to allow steam to escape.
Bake for 30-35 minutes, or until the crust is golden brown.