Tip the rice into a bowl and cover with cold water. Set aside to soak while you prepare the veg.
Peel and thinly slice the onions. warm a large pan or casserole dish for 2 mins over a medium heat. Add the onions with 2 tbsp oil and a pinch of salt. Pop a lid on the pan, turn the hat down and fry for xx mins, stirring every so often, till the onion is soft and golden.
While the onion fries, trim, peel and dice the carrots. trim and dice the courgettes to match. peel and grate the garlic and ginger. Halve the chilli. Scoop out the seeds and white pith (or leave them in for more heat) and finely chop them.
Stir the carrots, courgette, garlic, ginger and chilli into the onion. Sizzle for xx mins, stirirng now and then, till the veg start to brown.
Stir in 2 tsp garam masala and drop in the cardamom pods and cinnamon stick. Stir in the tamarind paste. Add another pinch of salt and a good grinding of black pepper.
Drain the rice and stir it into the pan. Pour in the coconut milk. Add 600ml boiling water and give everything a good stir to mix it well. Pop on the lid, turn up the hat and bring to the boil. Once the biriyani is boiling, turn the heat down and simmer for xx mins till all te liquid has been absorbed and the rice is tender.
Take the biriyani off the heat and let it sit the pan, lid on, for 5 mins to steam. This will finish cooking the rice and help make it fluffy.
Taste the biriyani and add a pinch more salt or pepper if you think it needs it. Fluff up the rice with a fork, then scoop the biriyani into warm bowls and serve.