Whisk together minced garlic, sesame oil, soy sauce, oyster sauce, Chinese white vinegar, and cornstarch slurry in a small bowl. Add thinly sliced beef and toss to coat, allowing it to sit about 10 minutes while you start preparing the rest of your ingredients. There is so much flavor going on with that beef-then it becomes tender at the end.
Scrape all the browned bits into a small bowl with the dark soy sauce, oyster sauce, black pepper, water, and potato starch, mixed together. Set aside.
In a large pot of boiling water, cook the udon noodles for 1-2 minutes, until slightly loosed-up but not overcooked, of course! Drain and set aside. No overcooking's necessary in this recipe-you want it still to retain just that little bit of bouncy chew!
Put the wok or large pan and heat it medium. Put one tablespoon of oil, Beef marinade is ready pan-brown until browned. That should take around 2-3 minutes because beef cooks fast so don't overcook it. Remove beef and set aside since you now need to work on the sauce
Used the same pan, put one tablespoon of oil, garlic, and onions sliced. Stir-fry until it is fragrant and softens. Add the cooked udon noodles and beef into the sauce. And the last add Chinese cabbage. Scramble everything in that pan really good so that everything's absolutely coated, too. Let everything toss one last time and you're good to go.
