Here is a vegetarian version I adapted of Rick Bayless' Pato Doradito Para Taquear, Estilo MP. It is a dish he presents as Asian Fusion on series four of his PBS show Mexico One Plate At A Time. My vegetarian version is the dish the Pedro requested for his latest birthday dinner.
This is how I make it. I make and simmer the soy sauce mixture as directed. While it is simmering, I wash and cut the vegetables. When the sauce is ready, I heat up some oil in a wok or other pan and add my assorted vegetables. I normally use shredded carrots, onion, green beans, mushrooms, red bell pepper or other pepper, and whatever other vegetable I have on hand. After sauteing to my satisfaction, I will add a bag of Quorn and the soy sauce mixture and let the dish simmer on low until the Quorn is heated and has absorbed the flavors and the vegetables cooked to my liking. However, if you prefer your veggies crispy, toss them with a bit of the soy sauce mixture and remove them before you add the rest of the sauce and the Quorn.
One way I serve them is to just make simple tacos of the vegetable/quorn mixture and Tomatillo Salsa on fresh corn tortillas. Another way, is to make tacos using fresh corn tortillas, refried black beans, the vegetable/Quorn mixutre and Tomatillo Salsa with cubes of avocado. Note: I do not prepare the tomatillo salsa in the manner that Bayless describes in this recipe, because I find uncooked tomatillos to be very harsh. If you follow his recipe, I recommend you boil or roast the tomatillos before putting them in the blender. Ovo vegetarian.