Preheat oven to 400 degrees
For Pie Crust, combine flour and salt. Cut in shortening until mixture resembles coarse meal.
Stir in water. Shape into ball.
Chill for an hour. Roll pastry to fit casserole dish.
For pie filling, saute onion, celery and carrot in butter for 10 minutes.
Add flour; cook 1 minute. Combine broth and half and half; gradually stir into vegetable mixture.
Cook over medium heat until thickened.
Stir in salt and pepper. Add chopped chicken.
Pour into a greased shallow 2 quart casserole. Top with pastry.
Bake at 400 degrees for 40 minutes.