Slice onions. Heat oil in a non stick wok, add onions and sauté.
Diagonally slice green chillies. When onions turn soft, add green chillies and continue to sauté.
Mix chicken with fish sauce, dark soy sauce and green curry paste and let it stand for 5 minutes.
Halve garlic cloves lengthways and add to the wok. Sauté for 10 seconds more.
Add chicken, salt and sugar and mix well. Cook on high heat for 1-2 minutes.
Add basil leaves and mix well. Cook till the chicken is done. Serve hot.