Make the crust: In a large bowl, mix the flour, salt, and oregano. Add the vegan butter and rub with your fingers just until it turns crumbly. Then add the soy milk and gently knead it to form a ball. Refrigerate for 30 minutes to solidify, then gently roll out or press the dough into a 9-inch baking dish or pie pan. Brush the pastry with olive oil to prevent a soggy-bottomed pie. Cover with parchment and dry beans to pre-cook the crust at 400F for 15 minutes. Then remove from the oven and take off the beans and parchment.
Make the filling: in a large pan, heat the olive oil over medium-high heat and add the onions and garlic. Cook for about 5 minutes, stirring frequently until it gets soft and translucent. Add the pepper, mushrooms, and oregano. Cook for 5-10 minutes more until most of the liquid that comes out of the mushrooms has evaporated. Add the spinach and let it wilt down. Let the vegetables cool slightly.
In a large bowl, mix the vegetables, Just Egg, salt, soy milk, flour, and crumbled tofu. Transfer to the pie shell. If it won’t all fit, you can save the rest of the filling to make a mini-omelette the next day. Bake at 375F for 45 minutes. Test for done-ness by sticking a knife in the middle of the quiche and checking that it comes out mostly clean. Cool for 15 minutes, then cut and serve warm. Top with vegan parmesan cheese if desired. Quiche is excellent as leftovers the next day too. Yum!