In your food processor, blend together the cilantro, garlic, fish sauce, oil, sugar and pepper flakes.  Pour the mixture over the chicken and mix it together so the chicken is completely covered on all sides with the marinade.  Cover and refrigerate for 1 hour.

15 minutes before the chicken is finished marinating, turn your grill on high and let it get hot.  After it has heated, grill the chicken, skin side down first.  Turn the heat down to medium and cook for 5-7 minutes.  Flip over the chicken and grill another 5-7 minutes on the other side, or until the juices run clear.