Finely grate the ginger and garlic. Mix these with all ingredients in a bowl then add the chicken pieces and coat them well with the marinade. Leave to marinate for minimum 30 minutes, longer if you can.
Heat you BBQ and cook the chicken leg pieces on medium heat for 25-30 minutes, turning regularly and brushing them with the marinade.
Slice the spring onions diagonally.
When the chicken legs are golden, charred (and cooked through!) put them on a serving plate, then scatter the spring onions around and sprinkle the sesame seeds on top.