Melt the ghee in a large, heavy-based pan on a medium heat. Add the cumin, bay and cloves, and fry for a few seconds. Add the onion and cook, stirring often, for 10-15 minutes, until soft. When the onions start to brown, move half of them to a plate.

Add the chillies and ginger to the onions left in the pan, fry for a minute, then stir in the tomato purée, chilli powder, coriander powder and turmeric, and fry for a minute. Turn the heat to low, stir in the yoghurt and cook for two minutes. Add the squash and mushrooms, stir to coat, then fry for three minutes. Add the stock, season and bring to a boil. Turn down the heat, cover and simmer for 20 minutes, stirring once halfway to make sure nothing's stuck to the bottom of the pan. Garnish with coriander, then take off the heat.

Heat the oven to 200C (180C fan)/ gas 6. Wash the rice and put it in a pan with a litre of water and the bay leaves, cardamom and salt. Bring to a boil, cook for 10-12 minutes, until three-quarters cooked, then drain.

Now build the biryani. Put a tablespoon of melted ghee in a heavy pot for which you have a tight lid. Ladle in half the squash mix, then top with half the rice. Add half the saffron water, ginger, mint, ground cardamom and garam masala, then add the reserved fried onions. Top with the remaining squash mix, then with the rest of the rice. Top with the last of the ghee, saffron, ginger, mint, cardamom and garam masala.

Cover with baking paper, top with the lid, then bake in the middle of the oven for 15-17 minutes, so all the flavours soak into the rice. Take out, leave to rest, still covered, for 10 minutes, then lift off the lid and serve with raita and salad.