If you are using dried noodles, cook for 4-5 minutes in a large pan of boiling water, If you are using fresh noodles, cook for 3-5 minutes in boiling water. Drain, then place in cold water until needed.
Heat a wok or large frying pan and add the oil. When moderately hot, add the garlic and ginger and stir fry for 10 seconds. Add the onion and fry to soften. Add