To the flank steak, add the Thai black soy sauce, vegetable oil, and cornstarch, and mix until the beef is completely coated. Set aside.
For the rest of the dish, combine the oyster sauce, sugar, Thai soy sauce, Thai black soy sauce, fish sauce, and white pepper in a small bowl. Stir to mix well.
Make sure your fresh rice noodles are at room temperature. If the noodles are really cold and stiff from refrigeration, rinse them quickly under hot tap water when you are ready to stir-fry the dish. This extra step will help you avoid a big homogenous lump of noodles during stir-frying. Be sure to shake off any excess water after rinsing and use them immediately.
The fresh wide rice noodles really set this dish apart from other noodle dishes, so try your best to find them. Or you can use our recipe for homemade rice noodles to make them at home. If either of these options don’t work, then use dried rice noodles. If using a dried rice noodle, follow the directions on the package and make sure you undercook the noodles slightly (al dente), since you will be cooking them again in the wok. After you drain the noodles thoroughly, toss the noodles with a tablespoon of oil. This will prevent them from sticking to the wok.
Heat your wok over high heat until it just starts to smoke, and spread 1 tablespoon of oil around the perimeter of the wok evenly to coat. Sear the beef until it is 80% cooked through, and transfer back to the marinade bowl.
Add another tablespoon of oil to the wok and stir in the garlic. Immediately add the Chinese broccoli and stir-fry for 20 seconds (stir constantly to prevent the garlic from burning).
Next, spread the noodles around the wok. Continue to work quickly--your wok should be at the highest heat setting. Spread the sauce mixture over the top of the noodles, and gently mix everything with your wok spatula using a scooping motion for about 20 seconds. Add the beef back to wok.
Push the mixture to one side to let the empty side of the wok heat for 10 seconds. Add another tablespoon of oil to the wok, and add the beaten eggs. Wait 5 seconds for them to begin to cook. Scramble the eggs for another few seconds, breaking them up into smaller pieces.
If your wok is not sizzling at this point, it probably means that your burner is not hot enough. Be patient, and the heat should “catch up.” Stir-fry the mixture just enough so the noodles heat up evenly, but don’t break into small pieces. Make sure you use your wok spatula to scrape the bottom of the wok so the noodles don’t stick.
As the wok heats up, you will notice that the food will stick to it less readily! But if you need to, you can add a little oil to make it easier to stir-fry.
Continue cooking, stirring less frequently (so the noodles get slightly caramelized, creating that restaurant-style flavor) for another 1 to 2 minutes, or until the noodles are heated through. Serve hot with Homemade Chili Oil or Chiu Chow Sauce on the side!