Remove the tough outer skin from the lemon grass and roughly chop. Place the lemon grass, ginger, garlic, onion, lime zest and juice, rice vinegar, sugar and olive oil in a processor and blend until smooth.
With a sharp pair of kitchen scissors or knife, make a deep cut into the thighs and to the bone on both sides of the drumsticks.
Place the marinade in a large bowl, add the chicken thighs and drumsticks and mix until coated. Cover and chill for at least 2 hours.
BBQ the chicken on a medium heat for about 15-20 minutes turning ever 5 minutes until the chicken is opaque with no trace of pink at the bone.
Serve the chicken and sprinkle with chopped coriander alongside a sweet chilli sauce dip.
Top tip: When BBQing, always make sure the chicken is cooked thoroughly before eating. To check this, pierce the plumpest part of the flesh and make sure the juices run clear. If not, cook further.