Rinse the rice 3 times and leave to soak
Make the chicken mix, place the chicken in a large bowl and mix with yoghurt and Biryani spice mix, the whole pack unless you like it less spicy for which add 3/4 pack. Set aside while you make masala base
Add oil and butter to a large pot and fry onions until well browned
Add tomatoes, chillies and water. Simmer on low heat for 15 mins
Zap up heat and bash the tomatoes with s spoon, add chicken mixture and keep stirring over a high heat

After 10 mins add potatoes, stir, lower heat, cover with lid and let it cook gently for around 20 mins or until chicken is done. There should be no surplus liquid and butter should have separated from masala (sauce)
If there seems to be too much liquid zap up heat and allow to boil off, don’t sure too hard for chicken will break. Taste and adjust seasoning, it should taste over salty and spicy.
Boil the rice in hot water with lots of salt and cardamon pods. The water should taste over salty.

Boil until the rice grain is long in length and nearly done. Drain rice and reserve.
Now to layer it all up, in a new large pot add a layer of rice in bottom, top with half chicken potato curry, add coriander then top with more rice. Repeat layers finishing with a layer of rice. Top this with fried onions and saffron.
Cover pot with a lid with a sheet of foil to keep steam in, press the foil on the sides of lid and pot and return to a very low heat for 15 mins
Zap up heat for 1 min then turn off and allow to sit for another 10mins
Open lid and lightly fluff up rice with a fork

Enjoy with some raita!