Heat oven to 400.
Line a 9 inch pie plate with pie crust.
In a 2 quart saucepan, melt butter over medium heat. Add onion and cook 2 minutes, stirring frequently, until tender. Stir in flour, salt and pepper until well blended. Gradually stir in broth and milk, cooking and stirring until bubbly and thickened.
Stir in chicken and mixed veggies. Remove from heat. Spoon into crust lined pie plate. Carefully top with second crust, seal edges and flute. Cut several slits in the crust to allow steam to escape.
Bake 15-20 minutes or until crust is golden brown. **Times will vary!!** If crust gets too brown on the edges, cover them with foil. Let stand 5-10 minutes before serving.