Soak the noodles in boiling water for 10 minutes, or until softened. Whisk the oyster and soy sauces, vinegar and sugar together and set aside.
While the noodles are soaking, heat the oil in a wok over a high heat, add the garlic and fry for 30 seconds, then add the chicken and stir-fry for 2 to 3 minutes until nearly cooked. Add the broccolini and a splash of water and cook for 2 to 3 minutes more.
Push the chicken and broccolini to the side of the wok and crack in the egg; scramble until just set, then mix with the chicken and broccoli. Remove from the wok and set aside.
Drain the noodles and add to the wok with the sauce and toss together to coat and heat through. Return the chicken and broccoli to the pan and mix together, then serve immediately.