Put the beef into a ziploc bag, whisk together soy sauce, dark soy sauce, sugar, potato starch, oil, sesame oil and rice cooking wine in a small container and pour over the beef into the bag, marinate for 15 minutes.
Bring a large pot of water to boil and cook the noodles for 2-3 minutes.
Strain the noodles, rinse them under cold water and then drain well.
Transfer the noodles back into the pot, mix with one tablespoon of dark soy sauce and set aside.
Heat a cast iron pan over high heat, carefully lay the beef onto the pan with a tong and sear for 1 to 2 minutes (cook without moving). Continue cooking while stirring for another 30 seconds to a minute, transfer to a plate and set aside.
Toss in soy sauce, oyster sauce, sugar, black pepper and red pepper flakes, continue cooking 2-3 minutes while stirring until everything is mixed well.
Transfer onto plates, sprinkle a touch of roasted sesame seeds on top and serve.
Notes
yakisoba noodle can be replaced with ramen noodle, lo mein or spaghetti.