Bring a large pot of water to a boil and add the chw mein noodles. Cook for 1 minute if using fresh, or 2-3 minutes if using dried noodles. Drain and rinse the noodles.
In a large wok over high heat, heat up the cooking oil. Add the noddles and spread out across the bottom of the wok. Cook the noodles for about 1 minute, and flip them over and cook for another. Repeat this process several times. We are working towards crisping up the noodles a bit.
When your noodles are cooked, put them into a large serving dish, and put the wok back on the burner.
In a small bowl, mix together the vegetarian oyster sauce, tamari, rice vinegar, Shaoxing wine, garlic, ginger and water. Set aside.
Put a tbsp of oil into the wok and add the broccoli, carrots, mushrooms, and onions. Stir fry for about 2 minutes.
Add the bok choy to the wok and mix the bok choy into the stir-fried vegetables, until the leaves have just begun to wilt.
Add the sauce to the vegetables and toss to coat. Cook for about 30 seconds, then add the vegetables and sauce to the top of the noodles and serve.