Start with the filling: Melt the butter in a large skillet over medium heat. Add the potatoes, celery, carrots, and onion. Cook, stirring occasionally, for 6-8 minutes or until the vegetables have softened and release some liquid. Stir in the flour, salt, pepper, garlic powder, thyme, and bay leaves until the flour has absorbed the liquid. Stir in the wine (or chicken stock), followed by the chicken stock and half-and-half. Simmer for 7-8 minutes or until thickened into a gravy consistency. Then, add the frozen peas, corn, and turkey. Allow the filling to cool for 5-10 minutes before transferring into the prepared pie dish.