Wash the basmati rice thoroughly and allow it to soak in cold water for 20 minutes.
Peel the onion and cut it in half lengthways, then slice it into half-moon shapes 3-5mm (⅛-¼") thick.
Heat a 28cm, 11" frying pan (not non-stick) over a medium-low heat, and when it is hot, add the cooking oil. Throw the onion into the pan and allow it to cook for 30-35 minutes, stirring every 5 minutes or so. If the onions begin to brown quickly, reduce the heat a little.
Add all of the ingredients for the rice into a small saucepan (15-16cm or 6") with the cold water and bring to a rolling boil.
Reduce the heat to a gentle simmer. Add the soaked and washed rice to the water and cover with a lid. Cook for 8-9 minutes, then remove from the heat and allow to steam with the lid on for 5 minutes.
Pierce the green chillies with the tip of a knife 3 or 4 times.
Peel the garlic cloves and mash them into a paste.
Peel and grate the ginger.
If you are using frozen peas, defrost them by running them under cold water.
By now, the onions should be nicely caramelised, transfer them to a bowl and put the pan back on a high heat.
Add the ghee to the pan and when it melts, throw in the green chillies, curry leaves, fennel, cumin and mustard seeds and cook for 1 minute, stirring constantly.
Add the garlic, ginger, turmeric, coriander and amchoor and stir for 30 seconds.
Throw in the minced lamb, salt and pepper, then cook over a high heat for 5-7 minutes, stirring regularly.
Add the cooked onions, tomato puree, jaggery, fenugreek leaves and dried pomegranate seeds, then pour in the water and cook for another 5 minutes.
Pick the large aromats from the cooked rice and discard them, then stir the rice through the minced lamb, cooking until the rice is piping hot.
Finally, add the peas and coriander and cook for a final minute, then serve.