Drain the broth from the seitan, if any, and pour into a soup pot or stir-fry pan. Cut the seitan into bite-sized chunks and set aside.
Cook the noodles according to package directions, then drain and cut into shorter lengths. Set aside until needed.
Meanhile, combine the broccoli, green beans, carrots, garlic, and baby corn with liquid, broth, mushrooms, and ginger to the pan. Bring to a rapid simmer, then lower the heat.
Add the seitan, then cover and simmer for 5 minutes, or until the broccoli and green beans are bright green and tender-crisp.
Put the cornstarch in a small bowl or mixing cup and stir in just enough of the liquid from the soup pot to smoothly dissolve it. Slowly pour into the soup pot and simmer just until the broth has thickened up. Stir in the soy sauce and noodles, and serve at once.