Place the Signature Cast Iron 24cm Casserole on a low heat and melt the butter with a splash of oil in the pan.
Add the onions with a pinch of salt and sprinkle in the allspice and cinnamon.
Fry the onions over a low heat for 5 minutes until soft.
Season the chicken legs with salt and generously cover with the sumac (or rub with the ½ a lemon) and chilli flakes.
Turn the heat up to medium and add the chicken to the onions. Fry the chicken legs on both sides for about 8 minutes until they begin to colour, being careful not to let the onions burn.
Stir in the sultanas and walnuts and drain the rice before adding it to the pan.
Season with salt, then pour over boiling water from a kettle so that the water comes 2cm above the rice. Cover and cook for 5 minutes, before turning the heat down to low and cooking for another 5 minutes.
Leave to rest off the heat for 10 minutes, then remove the lid and check that the chicken is cooked. If not, return to the heat or put into a hot oven for a few minutes>
Fork-up the rice to separate the grains and stir through the chopped herbs.
To serve top with the Greek yogurt and a scattering of pomegranate seeds and pistachios.