For the adrak lahsun ka masala/garlic and ginger paste
In a food processor blend the ginger and garlic together to a smooth paste. If necessary, add 15ml (1tsp) cold water. Store in a covered container in the refrigerator for up to 2 weeks.
For the biryani
Mix the lamb with the adrak lahsun ka masal, cinnamon, cloves, cardamoms, chilli, yogurt, lemon juice, 1 tbsp of the oil and the salt. Cover and refrigerate for 30-45 minutes.
Heat 3 tbsp of the oil in a small frying pan, and fry the onion for 5 minutes or until crisp and golden brown. Set aside. Rinse the rice thoroughly in cold running water and place in a pan with 400ml (14fl oz) boling water. Cover and boil for 8 minutes or until the rice is half cooked. The grains should be soft on the outside but still hard in the centre. Gently warm the milk and soak the saffron strands for a few minutes.
Preheat the oven to 180°C/350°F/gas mark 4. Heat the remaining oil in a heavy-based pan and fry the marinated meat for 15 minutes until well browned. Stir in the fried onion. rease the base of a large heavy-based casserole with the butter or ghee. Add the meat mixture followed by the par boiled rice. Pack the rice firmly into the casserole. Pour the saffron-laced milk over the rice. Cover tightly and bake for 45-50 minutes. Serve hot with mint chutney.