Using a sharp knife cut 3 deep slashes into the each chicken breast. Place them in a single layer in a baking dish.
Put the garlic, chilli, ginger, coriander, lime juice, soy sauce, castor sugar and coconut milk and process to a smooth paste in processor.
Spread the puree over both sides of the chicken portions, coating them evenly. Cover dish with cling film and leave to marinade in refrigerator for 1 hour.
Lift the chicken from the marinade, drain off the excess and place in a grill. Cook under a preheated grill for 12 – 15 minutes, until thoroughly cooked, (Cook time will depend on the size of fillets).
Meanwhile, place the remaining marinade in a wok or pan and bring to boil. Reduce the heat and simmer for 3 – 5 minutes to heat thoroughly. Remove the wok or pan from heat.
Place the chicken breast portions on warmed individual serving plates and pour over sauce. Serve immediately with boiled rice.