Heat half the olive oil in a large casserole dish then lightly brown the chicken on all sides over a medium heat (about 20 minutes). Remove and set aside. Add the remaining olive oil to the casserole dish and cook the onions until translucent (about 35 minutes under gentle heat), stirring occasionally. Add the Sumac and cook for a further 2–3 minutes until thoroughly mixed.

Preheat your oven to 170°C (325°F/Gas Mark 3). Entirely cover the base of a 22 x 30cm baking dish with 4 of the halved Arabic or pita bread. Spoon half the onions over the bread, arrange the chicken on top and cover with the remaining onions and the juices from the casserole dish. Cover with the remaining halves of bread ensuring that they're crusty side up. If possible tuck the sides in around the onions.

Spray the top of the bread with water to prevent burning and bake until the chicken is very tender and almost falling off the bone (About 1.5 hours.) Check the dish about an hour into the cooking time and before the bread starts to burn, spray with water again or cover with aluminium foil.