Heat oil in a wide skillet or wok over the highest heat possible until smoking. Add cabbage and toss aggressively until charred at the edges and just tender, 2–3 minutes. Don't overcrowd the pan. You want char, not steam.
Build the Sauce
Add garlic, soy sauce, dark soy sauce, oyster sauce, sesame oil, sugar, chili flakes, sesame seed, and stock. Toss continuously over high heat until the sauce coats every noodle and reduces slightly, 1–2 minutes.
Add the Noodles
Add fresh udon directly to the pan. Let sit undisturbed 30–45 seconds on both sides until the noodles warm up and loosen up on its own. Gently squeeze and shake to release the noodles the bottom catches and chars slightly.
Plate and Finish
Finish with scallions, sesame seeds, and a chili crisp drizzle. Add a fried egg on top if you want to make it a meal.