Heat oven to 425°. Prepare pie crust and place 1 crust in the bottom of a 9" pie pan.
Melt butter in medium saucepan over medium heat. Add onion, cook 2 minutes or until tender. Add flour, salt and pepper. Stir until blended. Gradually stir in broth and milk, cooking an dstirring until bubbly and thickened.
Add chicken and mixed vegetables. Mix well. Remove from heat. Spoon chicken mixture into crust-lined pan. Top with second crust and sel edges and flur Cut slits in top crust
Bake at 425° for 30-40 minute or until crust is golden brown. Let stand 5 minutes before serving.