Add the oil to a large wok or saucepan over a high heat and then fry the chicken until starting to brown. Turn the heat down to medium and add the onions next and stir everything together. Cook for around 3-4 minutes.

Add the tomato paste, spices and season well with salt and pepper. Add the stock cube, garlic and balsamic vinegar then pour over the cola. Give everything a good mix. Bring to a gentle simmer.

If you are adding chilli flakes, add them here. Add the green peppers. Simmer for 15-20 mins or until the cola sauce has reduced and become glossy and dark brown.