Photograph: Karen Thomas
Preheat the oven to 180°C, fan 160°C, gas 4. Toast the cumin and coriander seeds in a small frying pan; cool and grind.
Heat the butter and oil in a large ovenproof casserole dish until sizzling. Season the chicken.
Brown the chicken pieces in the hot fat, in batches, transferring them to a plate as they are ready.
Add the butternut cubes to the casserole, soften over a medium heat for 10 minutes. Stir in the ground spices, orange juice, lemon zest and juice, and the stock.
Bring to the boil and tip in the couscous, give everything a stir and return the chicken to the casserole. Cover with a lid and transfer to the oven for 1 hour.
Roughly chop the pistachio nuts and herbs. Transfer the chicken to a plate and keep warm in the oven. Stir the nuts, most of the herbs and the sumac into the couscous, check the seasoning and adjust to taste. Pop the chicken back on top of the couscous and scatter with the remaining herbs and the pomegranate seeds.
For more herbs and spices, click here