Mix all the ingredients for the marinade together in a medium bowl. Whisk and mix well.
Marinade the chicken thighs in a large bowl. Cover with cling wrap and set aside in the fridge for 30 minutes.
Pre-heat fan force oven to 180C or 350F.
Add all the onions evenly in a large non-stick baking tray lined with baking paper.
Add the marinated chicken thighs on top of the onion covering all the onion pieces.
Brush and add half of the marinate onto the chicken thighs and reserve the rest of the marinade.
Grill the chicken thighs bottom side up for 20 minutes and then turn the chicken thighs around. Brush and add the remaining marinate onto the chicken thighs. Grill for another 25 minutes or until chicken is cooked through.
Carefully pour all the sauce in the baking tray through a fine sieve into a medium bowl and reserve the sauce as a dressing for the chicken.
Serve the chicken with some steamed baby peas, sauce and steamed rice.