Boil noodles in sufficient water. Drain and cool. Heat oil in a wok, add onion and stir-fry for two minutes. Add carrot, capsicum and cabbage and stir-fry for two minutes, stirring and tossing continuously.
Add noodles, soy sauce, MSG, salt to taste and white pepper powder and cook on high heat for a couple of minutes or until the noodles are heated through, tossing continuously.
Add bean sprouts, mix well and serve hot garnished with spring onion greens.