Melt 4 tablespoons of unsalted butter over medium heat. Sprinkle in ⅓ cup of all-purpose flour while whisking continuously for 1-2 minutes until golden, to create a roux.

Gradually add 1 cup of chicken broth and 1 cup of milk, whisking to avoid lumps. Cook for 3-5 minutes until thickened. Fold in 2 cups of chicken and 1 cup of mixed vegetables. Season with onion powder, garlic powder, salt, and pepper.

Roll out one pre-made pie crust into a 9-inch pie dish. Pour filling into the crust, then top with second crust, sealing edges and cutting slits for steam.

Preheat oven to 425°F. Place pie on a baking sheet and bake for 25-30 minutes until golden brown.

Allow pie to rest for 10 minutes before serving.