In a 4 quart saucepan, add a tablespoon of oil or butter and the chopped onion, then cook until translucent.
Stir in frozen vegetables, chicken, chicken stock and spices. Turn up heat to allow the mixture to come to a boil.
In a small bowl, add the milk and cornstarch, then mix until smooth. Stir into the pot pie mixture on the stove. Continue boiling until the liquid has thickened. Taste and adjust seasoning, if needed.
Remove the pan from the heat and pour the chicken pot pie contents into an ungreased 9 x 13” casserole dish.
In a separate bowl, add topping ingredients and mix well. Spoon topping over the chicken mixture and smooth out to cover the surface.
Bake your gluten free chicken pot pie casserole for 25-30 minutes or until a toothpick inserted into the center of the casserole comes out clean. Sprinkle with fresh parsley as garnish, if desired, and serve while hot.