In a slow cooker, combine the shredded chicken, frozen mixed vegetables, cream of chicken soup, chicken broth, garlic powder, onion powder, thyme, pepper, and salt. Stir until well mixed.
Cover and cook on low for 4-6 hours or on high for 2-3 hours, until the mixture is heated through and the vegetables are tender.
About 30 minutes before serving, preheat your oven to 425°F.
Roll out one pie crust and place it in a 9-inch pie pan. Pour the chicken mixture into the crust.
Roll out the second pie crust and place it on top of the filling. Seal the edges by crimping with a fork or your fingers. Cut a few slits in the top crust to allow steam to escape.
Brush the top crust with the beaten egg for a golden finish.
Bake in the preheated oven for 25-30 minutes, or until the crust is golden brown.
Let cool for 5-10 minutes before slicing and serving.