I have made many, many tourtieres (meat pies). but instead of adding ingredients to make a gravy as the pie bakes, I use veggies diced fairly small to insure that they will cook all the way through. And I pre-brown the meat. The veggies are seasoned before they go into the pie crust.
Because the liquid content is small, I always have a tender and flaky crust on the bottom and top. I make gravy on the side from the meat juices accumulated while browning the meat.
With this method, you can even pre-cook the veggie ingredients before adding them to the pie. That way, you know the seasoning is correct.
Hope this helps.
Seeeeeeya; Goodweed of the North