In a slow cooker, combine the shredded chicken, frozen mixed vegetables, cream of chicken soup, chicken broth, garlic powder, onion powder, dried thyme, salt, and pepper. Stir until well mixed.
Cover and cook on low for 6-8 hours or on high for 3-4 hours, until the mixture is hot and bubbly.
About 30 minutes before serving, preheat the oven to 425°F.
Roll out one pie crust and fit it into a 9-inch pie pan. Pour the chicken mixture into the crust.
Roll out the second pie crust and place it over the filling. Trim and crimp the edges to seal. 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 it cool for 10 minutes before serving.