Heat the oil in a wok. Add the onion & curry paste and cook for about 1 minute stirring continuously. Add the coconut milk and water to the wok and bring mixture to the boil.

Add the chicken pieces to the wok, stirring to combine. Simmer, uncovered, for 15-20 minutes or until the chicken is tender.

Add the fish sauce, lime juice and sugar to the wok. Stir to combine.

Add the tomatoes 5 minutes before serving. Sprinkle with fresh basil leaves just before serving.