Prepare the pie dough if needed, per the instructions of the one you are using.
In a large stock pot, add in the butter, shredded chicken, chicken broth, and cream. Warm this up on medium-high heat to a low boil.
Once it begins to boil, reduce heat and whisk in the flour.
Mix in the vegetables and onion. Let this simmer on medium heat for about 10 minutes.
While the filling is simmering, begin to prepare the pastry dough. Spray a 9 inch pie pan and place one portion of the dough on the bottom. If you only have enough for the top, that is okay too. Be sure to cut it in the shape of the pan you are using.
Once you have the pastry dough covering the bottom of the pie pan, pour in the filling.
Cover the top with the remaining pastry dough.
Whisk together the egg and water.
Brush over the top of the pastry dough.
Bake in the oven for 1 hour or until nicely browned on top.
Cool for 5 minutes and serve.
Notes
If you are making this gluten free, I tend to purchase the King Arthur Flour Gluten Free Pie Crust Mix. This makes enough for both the top and bottom of the pot pie with one box of mix.