In a large bowl, combine the shredded chicken, frozen mixed vegetables, cream of chicken soup, chicken broth, garlic powder, onion powder, thyme, salt, and pepper. Mix well until all ingredients are evenly coated.
Pour the chicken mixture into the slow cooker, spreading it evenly.
Roll out one pie crust and place it over the chicken mixture in the slow cooker, tucking the edges down around the sides. Cut a few slits in the crust to allow steam to escape.
Roll out the second pie crust and cut it into strips or shapes for a lattice top, if desired. Place it over the first crust or simply lay it flat.
Brush the top crust with the beaten egg to give it a golden color while baking.
Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the crust is golden and the filling is bubbly.
Once cooked, let it cool for about 10 minutes before serving.