In 2-quart saucepan, melt butter over medium heat. Stir in flour, onion, salt and pepper. Cook, stirring constantly, until mixture is bubbly; remove from heat. Stir in broth and milk. Heat to boiling, stirring constantly. Boil and stir 1 minute. Stir in chicken and peas and carrots; remove from heat.
Heat oven to 425F. Roll 1 pie crust into 13-inch square. Ease into ungreased 9-inch (2-quart) glass baking dish. Pour chicken mixture into crust-lined dish.
Roll remaining pie crust into 11-inch square. Cut out designs with 1-inch cookie cutter. Place square over chicken mixture. Arrange cutouts on top crust. Turn edges of pie crust under; flute edge.
Bake about 35 minutes or until golden brown.