Place all of the barbecue sauce ingredients in a bowl and whisk until combined. Set aside.
Preheat your oven to 180°C. Heat some olive oil in a deep frying pan. Sauté the red onion, paprika and cumin together for a three minutes. Add the chicken thighs and season with salt and pepper. Toss the chicken to coat in the spices.
Transfer the contents of the saucepan to an ovenproof dish. (Try and use one that allows the chicken to fit snugly in a single layer.) Pour the barbecue sauce over the chicken.
Cover the oven dish with foil and bake for one hour. Transfer the chicken to a chopping board. Take the chicken off the bone and shred. Place the shredded chicken in a bowl. Add one cup of the barbecue sauce from the oven dish and mix well.
Spread the barbecue chicken over four flour tortillas. Add a sprinkling of cheddar cheese and chopped coriander. Place another tortilla on top of each one.
Heat a frying pan over a medium heat. Dry fry each tortilla for a minute on each side. Cut into wedges and serve immediately with some sour cream.