Preheat oven to 375°F.
Line pie dish with bottom crust.
Heat butter in large skillet over medium heat.
Add onion and celery to hot butter.
Cook vegetables until soft, about 5 minutes.
Sprinkle flour over cooked vegetables evenly.
Stir constantly for 2 minutes until combined.
Gradually add cream and chicken broth slowly.
Whisk mixture until smooth and thick sauce forms.
Add shrimp, seasonings, and parsley to sauce.
Cook shrimp for 3-4 minutes until pink.
Pour hot mixture into prepared pie crust.
Cover with top crust and seal edges.
Cut small vents in top crust surface.
Brush beaten egg over entire top crust.
Bake for 35-40 minutes until golden brown.
Cool for 10 minutes before serving slices.