Rose garam masala leg of lamb (masaladar raan)

1 Heat 3 tbsp oil in a large frying pan over a high heat, then, once hot, fry ½ the onion (don’t overcrowd the pan), keeping it moving so it turns medium brown and crispy (about 6-8 minutes). Line a plate with kitchen paper; spoon the onion out onto it with a slotted spoon before it turns very dark – the residual heat will continue to brown it once out of the oil. Add 2-3 tbsp more oil to the frying pan and fry the remaining onion in the same way, then transfer to the plate; set aside to cool. Finely grate ½ the garlic cloves and put in a small blender along with the cooled onions, ginger and 2 tbsp water; whizz until blended, then set aside.

2 For the rose garam masala, heat a small frying pan and toast the cumin seeds for about 1 minute, until dark brown; cool. In a spice blender or with a pestle and mortar, grind all the spices (including the toasted cumin) and rose petals into a fine powder.

3 Use a small sharp knife to score the top, fatty side of the lamb. Press the remaining garlic cloves into the scored lines on the lamb. Rub all over with the yogurt. In a bowl, mix the tamarind, whizzed onion mixture, salt, 3 tbsp of the rose garam masala (reserve any left over to serve), the coriander and chopped chillies and mix well. Put the lamb in a roasting tin or on a platter and cover with the marinade. Rub it into the meat well, especially into the scored lines. Cover and chill for at least 3 hours, or ideally overnight, for the best flavour.

4 Take the lamb out of the fridge 20 minutes before cooking to allow it to come to room temperature. Preheat the oven to 180ºC, gas mark 4. Put the lamb in a large roasting tin and cover loosely with foil. For medium, cook for 2 hours 10 minutes, or for well-done, cook for 2 hours 50 minutes, basting halfway through. Remove the foil for the final 10 minutes to brown, basting again. Let the lamb rest for 30 minutes, covered with the foil. Serve scattered with rose petals, coriander and any leftover garam masala, with lime wedges on the side.