Put the red wine vinegar, salt and sugar into a small saucepan over a medium heat. Cook gently, stirring, until the salt and sugar have dissolved. Remove from the heat.
Peel and finely slice the onion. Place in a bowl. Pour the vinegar mix over the onion, making sure it is all covered by the liquid. Cover with foil and leave at room temperature for two hours. If you are not using them immediately, transfer to the fridge after two hours.
For the chicken
Put the yoghurt, smoked paprika, chilli flakes, ground cinnamon and garlic powder into a bowl. Mix well.
Place the chicken thighs on a baking tray. Use your hands to rub the yoghurt mix all over each chicken thigh, placing them skin side up on the baking tray when done. Make sure you use all of the yoghurt mix. Transfer the baking tray to the fridge for an hour.
For the garlic mayo
Put the mayonnaise and garlic powder into a bowl. Mix well. Leave to one side.
To make the kebabs
Preheat the oven to 200 degrees C.
Put the baking tray with the chicken thighs into the oven for 40 minutes, or until cooked through.
Halfway through the cooking time, lay the French fries on another baking tray and put on the top shelf of the oven for 20 minutes.
Cut the cucumber in half lengthways and slice into pieces the thickness of a one pound coin.
When you are ready to serve, lay your flatbreads on plates. Top with a spoonful of pickled onions and cucumber. Remove the chicken for the oven and use forks to pull the meat away from the bone. Add the meat to your flatbreads. Top each with a handful of fries and a drizzle of garlic mayo.