Using a mortar and pestle, pound the red chillies, garlic and coriander leaves into a coarse paste; keep aside.
Heat 3-4 tbsp oil in the wok and add the chicken pieces. Stir fry the chicken pieces on high heat till 3/4ths done and remove.
In the same wok (add a bit more oil if necessary), add the pound chilli mixture and sauté on low heat for about a minute. Add the oyster sauce, fish sauce and whole green chillies; also return the chicken pieces to the wok.
Stir fry on medium heat till done; add salt only if necessary.
Garnish with coriander leaves and spring onions