Preheat the oven to 180°C/gas mark 4

Coat the inside of the pumpkin with the tamarind paste, sprinkle with the chilli flakes and place on a rack and roast in the oven for approximately 25 minutes, until tender but still holding its shape

Soak the rice in cold water for approximately 10 minutes, then drain

Meanwhile, prepare the Jerusalem artichokes for the vegetable filling by peeling and cutting into a 1cm dice and squeezing over some lemon juice

Mix together the marinade ingredients in a flameproof casserole dish, but include only half the mint

Stir in the chopped green beans, the mushrooms and vegetables for the filling and set aside to marinate for 15 minutes

Meanwhile, add the water and boiling spices to a large saucepan and bring to the boil

Add the drained rice and boil, uncovered, for 6–8 minutes, until the rice is not quite cooked. Drain well

Place the warm milk and saffron in a bowl and leave for 3–5 minutes to infuse. Stir in the oil and rosewater essence and set aside

Once the vegetables have marinated, place the casserole dish over a low heat and simmer for 5 minutes, stirring constantly until the vegetables are half-cooked

Layer the rice over the simmering vegetables, pour over the saffron mixture and sprinkle with the remaining mint

Cover the casserole pan, increase the heat to high and leave to cook for 5–7 minutes - this will allow the steam build up

As soon as the steam starts escaping from the pot, reduce the heat to low and cook for another 8–10 minutes. Remove the casserole from the heat and leave to rest for 5 minutes

Transfer the biryani to the pumpkin shell. Chop the remaining green beans into 1cm pieces and sprinkle them over the biryani. Cover with the reserved pumpkin lid

Place on a baking tray and roast in an oven set to 200°C/gas mark 5 for 15 minutes

Remove the pumpkin from the oven, take off the lid and serve immediately