Method

1. For marinating the chicken, make 2 slashes across each chicken thigh with a sharp knife. This helps the marinating ingredients seep into the meat. Place the thighs, in a single layer, in a ceramic dish

2. Mix the lemon juice and chilli powder and spoon over the chicken, coating well on both sides. Leave on one side for 20 minutes.

3. Heat a small heavy-based pan or griddle over a moderate heat and toast the cumin seeds, stirring all the time, until they give off a lovely nutty aroma - this doesn't take long - about 30 seconds.

4. Tip the cumin seeds into a mortar and pound with a pestle until they are ground to a powder. Don't worry if it isn't too fine.

5. Roughly chop the garlic cloves, ginger and onion and grind in a food processor until smooth - you might need to add a spoon of yogurt to help it on its way.

6. Stir in the remaining yogurt, garam masala, coriander and half of the ground cumin. Reserve the remainder for the sauce. Season with salt.

7. Pour this yogurt marinade over the chicken thighs. Cover with plastic wrap and chill overnight in a refrigerator. If you can, turn the chicken once while it's marinating.

8. The next day, preheat a grill to its hottest setting with the grill-pan in place.

9. Take the chicken out of its marinade and arrange the pieces on the preheated grill pan. Grill near the top of the grill for 3-5 minutes on each side - until tender and beginning to char around the edges. Remove from the grill, save any cooking juices, and keep warm while you make the sauce.

10. For the sauce, whisk the tomato puree with enough hot water to make up the volume to 200ml. Stir in the cream or Greek yogurt, coriander, ginger, sugar lemon juice and reserved cumin.

11. Melt the butter in a frying pan and pour in the sauce. Bring to a simmer, stirring, and when hot, add the cooked chicken pieces and accumulated juices. Season to taste, reheat and serve with a stack of naans or freshly boiled rice.