This is an adaptation from a recipe on the back of a can of veg-all. The original recipe only called for 1 15 oz. can of veggies, and 2 cans of cream of potato soup, along with chicken. I have added more veggies, am making my own cream of mushroom soup, and of course use vegan chicken. This version is much healthier, and in my opinion, tastier.
If you don't like mushrooms, you can make the sauce/soup any flavor you wish by adding celery, or whatever you like.
Preheat the oven to 400 degrees. In a medium frying pan, place the frozen mixed vegetables along with the water, and cook on medium heat until almost done. While the vegetables are cooking, melt the margarine in a small sauce pan. Slowly add the flour while stirring with a whisk so it doesn't get lumpy. Slowly add the milk and continue to stir. Once it starts bubbling, turn the heat down to simmer and stir often until the mixture thickens like cream soup. Add the onion powder, herbs de provence, mushrooms (if desired), and salt. Turn the heat off.
Drain the vegetables in a colander and then place them in a large bowl. Add the chicken to the bowl and then the sauce. Mix thoroughly and carefully fill one of the pie shells with everything in the bowl. Carefully turn the second pie shell upside down and put it over the top of the pie, trying to place the edges over the edges of the bottom shell. Pinch the edges together and make a hole in the top for steam to escape. If you are using pre-made pie crusts from the freezer section of your grocery store, it's easier to keep the crusts in the freezer until you are ready to assemble the pot pie. Place the pie on a cookie sheet covered with parchment paper or foil for possible spilling while cooking. Cook in the middle of the oven for 45 minutes or until the filling is bubbly, and the top crust is brown.