In a large saucepan over medium heat, add ⅔ stick butter, onion, celery, and carrots and cook until tender (about 5 minutes). Add ⅓ C flour, ½ t salt, ½ t pepper, ¼ t thyme, 1 t dried parsley, ½ t garlic powder, and 1 t chicken bouillon powder and cook for about 1 minute.

Next, slowly add the 1½ C water and 1 C milk as the mixture continues to thicken - this should take anywhere from 5 - 10 minutes. Add the peas, chopped chicken, and ½ t worcestershire sauce. Cook for an additional few minutes, then turn off the heat and allow mixture to cool down.

Preheat oven to 425° F.

Generously grease the bottom and sides of a 9" pie pan. Place one of the pie crusts carefully into the pie plate, ensuring it completely covers up to and over the rim of the pie pan. Spoon the filling into the pie plate and smooth to even out. Carefully place the second pie crust over the top. Use a knife to cut off any excess dough and press the pie crusts edges together. Use a fork to crimp and further seal and cut a slit in the middle to allow steam to escape while cooking.

Whisk the 1 egg in a small bowl and brush over the top of the crust. Place in the preheated oven and bake for 45 - 50 minutes or until crust is golden brown. Allow to cool for at least 15 minutes before serving.