Cut the chicken thighs into 4cm pieces. Mix the marinade ingredients together in a bowl. Add the chicken and season liberally with salt and pepper. Mix well and leave to marinate for 1–2 hours. Finely shred the red cabbage, toss with the lemon juice and set aside to pickle.
For the sauce, put the garlic bulb on a piece of foil, drizzle with a little of the olive oil and wrap to seal. Place on the hot barbecue with the onion and peppers. Cook, turning the veg carefully for 10 minutes, then add the tomatoes and chillies and cook all the veg until charred all over. As each item is cooked, transfer to a bowl; keep tightly covered with cling film.
Let the charred veg steam in the bowl for 5–10 minutes, then remove and peel away their skins. Halve and deseed the peppers and chillies then chop all the veg finely and place in a bowl. Squeeze out the flesh from 4 roasted garlic cloves, finely chop and add to the veg. Mix in the sherry vinegar, olive oil and a little seasoning.
For the tahini yoghurt, squeeze the flesh from 2 roasted garlic cloves and chop finely. Mix with the yoghurt, tahini, lemon juice and salt and pepper to taste.
Thread the chicken onto 6 metal skewers. Barbecue for 4–5 minutes on each side. Also, heat the flatbreads on the barbecue, for 1–2 minutes on each side. Serve the chicken skewers with the warm flatbreads, chilli sauce, pickled cabbage, tahini yoghurt and pickled chillies.