Cut the chicken thighs into ⅓cm-thick strips. Cut the carrots and peppers into 5-7cm-long strips and a similar thickness to the chicken. Peel and thinly slice the onions.
Cook the noodles according to the instructions on the packet – wash the cooked noodles in cold water, drain and set aside.
Heat the empty wok to smoking temperature – this may take a minute or so depending on your wok. Add the oil followed immediately by the strips of chicken – turn the chicken in the wok to ensure all sides are sealed.
Cook for another 2 to 3 minutes to make sure the strips are cooked. Add the salt, pepper and garlic, and the sliced onions, carrots and peppers, and stir fry with the chicken for 3 minutes.
Add the drained noodles, soy sauce and sugar, and cook for a further 2 to 3 minutes. Taste and adjust the seasoning. Serve garnished with the spring onions.