I wish I was writing this down as I was making it. The filling tastes amazing. I am going to kind of guess as to how I made it because it is worth making again.
rehydrate 1/2 a cup of TVP (bob's red mill) by adding 1/2 cup of boiling vegetable stock and let it sit covered for 10 minutes
in a med sauce pan saute 1 small onion in 3 tbsp olive oil until they are transparent. Add 2 medium chopped carrots, 2 small cubed potatoes, and 1 cup of chopped button mushrooms let this sit covered for maybe five minutes on low heat so that the carrots and potatoes get soft. You can add a little vegetable stock (maybe 1/4 c) to it if you are worried about it burning and sticking to the bottom of the pan.
I then added the TVP a little more vegetable stock a large handful of frozen peas, and added sea salt, garlic powder and black pepper to taste. I mixed about a tablespoon of flour with another 1/4 c of stock until it was well mixed and added that to my pot to make it a little thicker. I pretty much arbitrarily added stock till it "looked right" so nothing is exact.
Preheated the oven to 350. I oiled an 8 by 8 in pyrex baking dish, whipped togeter an "easy" pie crust (for a 1 crust pie) that needed to be refridgerated for one hour and I froze it for maybe five minutes. I dumped what was in the sauce pan into the baking dish, topped with the crust and popped it into the oven where it is now. I am thinking I'll bake it for about twentyfive minutes. The reason I know this well be good is because I was snacking on the filling while I was making it and it is delicious! Next time I make this I am going to try and write down something a little more exact.