Dice the chicken breasts and place them into a large bowl.
Mix together a quarter of a cup of orange juice, one teaspoon of dark soy sauce, one teaspoon of light soy sauce and one teaspoon of rice vinegar.
Add the marinade to the chicken pieces together with half of the amount of garlic and ginger and leave to marinate for 5 minutes.
Discard of the marinade, and coat each piece of chicken with corn flour, shaking off any excess flour.
Heat up the vegetable oil in a wok over a high heat, add the coated chicken pieces and stir fry for about 2-3 minutes on each side, until lightly brown and cooked through.
Remove the chicken from the wok and set aside.
Cut the spring onion finely, and add the white part to the wok together with the remaining garlic and ginger.
Stir fry for about 30 seconds, then add the chicken back.
To make the orange sauce, mix one teaspon of corn flour with one teaspoon of cold water and stir well to get a lump-free mixture.
Add it to a bowl together with the remaining orange juice, soy sauces, sesame oil and rice vinegar. Mix well to combine.
Pour the sauce over the chicken pieces and stir fry for about a minute, so that the sauce can cook and stick to the chicken.
Serve with the green bits left from the spring onion.