Method
Cut the chicken breasts into roughly equal pieces (you need them to be large enough to stay on a skewer, but small enough to eat comfortably). Trim the peppers, remove the seeds and cut them into evenly-sized pieces (as above), then trim and peel the onion and cut into pieces the same size as the peppers. Finally, remove the skin and woody core from the pineapple (if using) and chop it into skewer-friendly cubes, then put the pineapple, meat and vegetables into a shallow dish.
In a large bowl or jug, whisk all the marinade ingredients together until well combined, then check the seasoning. Pour half of the marinade over the chicken mixture and use two spoons to turn everything over a few times, until well coated. Cover the dish with clingfilm and leave in the fridge for at least four hours. Refrigerate the unused half of the marinade separately. When you want to start barbecuing, light the charcoal and lightly oil the grate. Wait for the coals to become properly hot (usually this is when they have become grey, with a light coating of ash). To assemble the skewers, drain off and discard the marinade that was in the dish with the chicken, then thread the meat, veg and pineapple alternately on to skewers until you have used everything up. Put the kebabs on the hot barbecue and use the other half of the marinade to baste them, turning them every so often until the chicken is cooked through and the vegetables have softened and started to pick up nice charred edges. As a guide, this will take 10-20 minutes – any meat juices will run clear when the chicken is cooked. Serve with warm pittas, salad leaves and sunshine!