1. Place noodles in a large heatproof bowl. Cover with boiling water. Stand for 2 to minutes or until tender. Drain. Rinse under warm water. Combine arrowroot and 2 tablespoons cold water to form a paste.
2. Heat a large wok over high heat until hot. Add 2 teaspoons oil and swirl to coat base and sides. Add one-third of the chicken and stir-fry for 1 minute or until golden. Transfer to a plate. Repeat with oil and remaining chicken in 2 batches.
3. Add remaining oil, ginger and garlic to wok. Stir-fry for 30 seconds. Add onion and stir-fry for 1 minute or until tender. Return chicken and any juices to wok.