1. In a food processor, combine the flour and salt. Add the cold vegan butter and pulse until the mixture resembles coarse crumbs. Slowly add the ice water and pulse until the dough just comes together. Divide the dough into two equal discs, wrap in plastic wrap, and refrigerate for at least 30 minutes.

2. Preheat your oven to 375°F (190°C).

3. In a large skillet, heat the olive oil over medium heat. Add the onion and sauté for 5 minutes until translucent. Add the garlic, carrots, celery, and mushrooms, and continue to cook for another 5-7 minutes, stirring occasionally, until the vegetables are tender.

4. In a small bowl, whisk together the vegetable broth and cornstarch until the cornstarch is dissolved. Pour the broth mixture into the skillet with the vegetables, then stir in the peas, lentils or plant-based meat, thyme, and sage. Season with salt and pepper to taste. Bring the mixture to a simmer and cook for 5 minutes, or until the sauce has thickened.

5. On a lightly floured surface, roll out one of the dough discs into a circle slightly larger than your pie dish. Gently transfer the dough to the pie dish, pressing it into the sides and bottom. Pour the vegetable filling into the crust.

6. Roll out the remaining dough disc and place it over the filling. Crimp the edges to seal and cut a few slits in the top crust to allow steam to escape.

7. Bake the pot pie for 35-40 minutes, or until the crust is golden brown and the filling is bubbling. Allow the pie to cool for 10-15 minutes before slicing and serving.