Vegetarian Mongolian Beef is a meat-free alternative that is just as delicious and satisfying. Instead of beef, this recipe uses tofu or seitan as the main protein source. The tofu or seitan is marinated in a mixture of soy sauce, ginger, garlic, and other seasonings to infuse it with flavor. It is then stir-fried with green onions and a savory sauce until it is caramelized and coated. Serve this vegetarian version over rice or noodles for a tasty and filling meal.