Cook the noodles in a large pan of boiling water for 3-5 mins, then drain and put them in cold water for 2 minutes. Drain again thoroughly and set them aside.
Pop the sliced chicken into a bowl. Add the egg white and the Oyster sauce. Massage the egg and oyster sauce into the chicken ensuring everything is coated. Set the bowl aside.
Heat a large lidded wok or a deep frying pan set over a medium heat. Spritz with some low calories cooking spray. Add the crushed garlic and fry a minute. Add the 50ml of the Chicken stock, onion, mushrooms and carrots. Stir together and stir fry for for 2 - 3 minutes.
Keep the pan on a medium heat, add the marinated chicken. Brown the chicken, if it starts to stick add a little more spray or water.
Turn off the heat, add both soy sauces, rice vinegar, white pepper, sweetener and rest of the chicken stock. Stir gently then turn the heat back on to high and cook for 1 minute.
Add the egg noodles and, using tongs, gently toss for about 15 seconds to make sure they're thoroughly coated with the sauce.
Add the spring onion, toss together. Pop the lid on and steam on a medium heat for 2 minutes.