In a skillet, melt butter over medium heat. Stir in flour, salt, pepper, and onion powder until well blended.
Gradually stir in broth and milk, cooking and stirring until bubbly and thickened.
Stir in chicken and mixed vegetables. Remove from heat.
Place one pie crust in a 9-inch pie plate. Pour chicken mixture into crust. Top with second crust; seal edges and cut slits in several places on top crust.
Bake in preheated oven for 30-35 minutes, or until crust is golden brown. Let stand 5 minutes before serving.