Preheat oven to 170°C.
To make the pilav, heat oil and 1 knob of butter in a medium-large pot and cook onion, garlic and spices until onion is soft (4-5 minutes). Add currants, orange zest, rice, pine nuts, stock and a good pinch of salt, cover and bring to the boil. As soon as it starts to boil, reduce to low heat, cover and cook for 15 minutes. Turn off heat and leave to steam (still covered) for 10 minutes. Fluff up rice with a fork and toss through remaining knob of butter and herbs.
To cook the chicken, mix cumin, cinnamon, sumac and salt together. Place chicken in a roasting dish, breast side up. If you like, you can stuff the chicken with about one-third of the pilav (reserve the rest for serving) or just leave chicken as is. Drizzle with olive oil and rub spice mix all over. Tie legs together. Roast for 1 hour 10 minutes or until chicken is just cooked through (the juices will run clear). Cover with foil and leave to rest for 15 minutes.
Place pomegranate juice, balsamic vinegar and orange juice in a pan and bring to a boil. Add any cooking juices from the roasting pan and simmer rapidly for about 10 minutes until reduced to a sauce.
Transfer chicken to a platter and spoon remaining pilav around chicken. Serve with pomegranate sauce on the side.