Place all sauce ingredients in a food processor. Process well to form a thick curry paste or sauce.
Do a taste test for salt and spice, adding more fish sauce if not salty enough. If not spicy enough, add more fresh chilli. If too sour, add a little more brown sugar.
Place sauce in a wok or large, deep-sided frying pan over medium-high heat. Add chicken pieces and stir well.
Continue stirring occasionally as you bring the curry to a boil. Then reduce heat to a bare simmer. Do not cover the wok/frying pan, as you want the sauce to reduce and become thicker.
Allow the curry to simmer (stirring occasionally) for up to one hour, or until meat is cooked and tender. The sauce will reduce, so that it is almost like a coating on the meat (plus there will be a little sauce in the wok/pan).
Garnish with a sprinkling of shredded coconut and fresh coriander (if desired). Serve hot with jasmine rice.