Unroll one pie crust; fit into 9-inch pie plate that has been coated with cooking spray.
Melt butter in a large saucepan over medium heat. Add flour; cook and stir 1 minute. Add milk; bring to a simmer, stirring frequently. Add vegetables; simmer 3 to 4 minutes or until vegetables are hot and sauce has thickened. Stir in salt and pepper. Remove from heat; stir in chicken, cheese and parsley. Spoon mixture into pie crust-lined plate. Top with second pie crust; fold edges under bottom crust and crimp to seal. Cut several slits in crust to vent.
For optional glaze, brush beaten egg lightly over crust. Discard any remaining egg. Bake in a preheated 425°F oven 35 minutes or until crust is deep golden brown.