Heat oven to 450 degrees F. Coat bottoms of two 9-inch glass pie plates with nonstick cooking spray.
Combine flour and broth; place in a large pot. Bring to a boil; add milk and celery. Simmer 3 minutes. Stir in chicken, vegetables, onion flakes, parsley, poultry seasoning, garlic salt and pepper.
Spoon chicken mixture into pie plates.
Unroll pie crusts, placing one on top of each pie plate and crimping edges.
Before baking, vent and lightly brush with beaten egg. Bake at 450 degrees F for 15 minutes; reduce heat to 350 degrees F and bake for an additional 25 to 30 minutes or until filling is bubbling and crust golden.
Allow to cool slightly before serving.