Heat the oven to 200C/180C fan/ gas 6. If you’re making the spice mix, combine all the ingredients and set aside. For the sauce, tip the onion, garlic, chilli and ginger into a food processor and blitz until smooth. Heat the oil and ghee or butter in a large frying pan over a medium heat and fry the spiced onion purée with a pinch of salt for 12 mins. Add 2 tbsp of the spice mix, turn up the heat to high and cook for 1 min. Tip in the tomatoes, sugar and 250ml water. Bring to a simmer. Season well with salt and turn off the heat.
To prepare the chicken, put the remaining spice mix in a bowl with 1 tsp sea salt and the ghee or butter, and mash together. Push two-thirds of the spiced butter beneath the skin of the chicken breasts, then rub the rest over the outside of the breasts and legs. Season the chicken skin with 1 tsp sea salt and tie the legs together. Sit the chicken in a 28-30cm pan, shallow casserole or roasting tin and pour the sauce around the bird. Cover the chicken with foil and roast for 40 mins, then remove the foil and roast for another 30-40 mins, or until cooked through (when you cut into one of the legs, the juices should run clear). Stir the double cream into the sauce. Taste for seasoning and leave to rest, uncovered, for 10 mins.
Make the chutney by blitzing all the ingredients together in a food processor until coarse. Season to taste.
Top the chicken with some extra sliced chillies and coriander leaves, then serve with the chutney, pilau rice and naan, if you like.
