Optional - velveting the chicken (see notes): Combine chicken and baking soda in a small bowl and toss to combine. Set aside for 10 minutes to marinate, then rinse chicken well and pat dry.
Chow Mein Sauce (if using): Mix together cornflour and soy sauce, then mix in remaining ingredients.
Pour 1 tbsp of Chow Mein Sauce OR Real Chinese All Purpose Stir Fry Sauce over the chicken and set aside to marinate for 10 minutes.
Prepare the noodles according to the packet instructions.
Heat oil in wok or large fry pan over high heat.
Add garlic and stir fry for 30 seconds until the garlic is golden brown and you can smell the garlic in the oil. Remove garlic from wok.
Add chicken and stir fry until the skin is white but the inside is still raw - about 45 seconds to 1 minute.
Add the cabbage, carrot, and the white pieces of shallots/scallions (i.e. from the base of the stalk). Stir fry for 1 - 1½ minutes until the cabbage is just starting to wilt and the chicken is cooked through.
Add the noodles, Real Chinese All Purpose Stir Fry Sauce/Chow Mein Sauce and water. Stir fry for 1 minute, tossing to coat the noodles in the sauce.
Add bean sprouts and remaining shallots/scallions. Stir through quickly then remove from heat.
Serve immediately.