Start by making the crust (or use store-bought): Make your ice water by adding your water to a glass with ice. Mix in the vinegar and set aside as you prepare the rest of the dough.
In a medium bowl, mix the flour and salt. Add the butter and cut into the flour using a pastry cutter or fork. The butter should be the size of large peas.
Add 1 tablespoon of the cold water/vinegar to the flour mixture at a time. You should need 2-3 tablespoons. You don’t want the dough to be overly moist, but it should just hold together when pressed.
Place the dough onto a lightly floured surface. Lightly press the dough to form a rectangle using your hands or a rolling pin. Fold the dough, one side to the center, then the other. Flatten, then repeat this step 2 more times. This helps you get a flaky crust.
Keep the dough folded, wrap it up and let it cool in the fridge while you prepare the rest of the recipe.
Prepare the filling: In a large saucepan, heat oil over medium heat. Add the onion and garlic and cook for 5 minutes. Add your celery and carrots and cook for another 2-3 minutes, then add mushrooms. Sprinkle with salt and pepper and continue cooking until the mushrooms have softened, about 5 minutes.
Sprinkle the vegetables with flour. Add the potatoes, black eyed peas, broth, almond milk, bay leaves and thyme. Bring to a boil, then simmer, covered, over low-medium heat for 10 minutes or until the potatoes are fork tender.
Pour the vegetable mixture in a 9 inch pie pan. Don’t fill the pan more than ¾ of the way.
Take the dough out of the fridge and roll it out into a large circle. Cover the vegetable mixture with the dough. Using a knife, cut a small hole in the center. Lightly brush with an egg wash if desired (this helps the crust get nice and golden).
Bake for 35 minutes.