Prepare the udon noodles according to the packet directions (usually soaked in boiling water for a few minutes), then drain in a colander.
Heat the oil in a large non-stick frying pan over high heat.
Add the garlic, bean sprouts, kimchi cabbage and the white part of the green onion. Cook for 1 minute until the bean sprouts are almost wilted.
Add the green part of the green onion, the noodles and all the sauce ingredients. Toss for 2 minutes until the sauce stains the noodles.
Transfer to a bowl, sprinkle with sesame seeds (if using), then devour.
