Preparation
Wash and soak rice in water for 20 to 30 minutes (If you are really in a hurry, just soak it till you get other things prepared).
Grind to paste, ginger, garlic, laung, choti elaichi, dal chini, kali mirch (take half of these spices, keep remaining to flavour the rice).
Wash and clean the prawns, also de-vein them. Marinate in salt, turmeric powder and red chilly powder. No need for very long marination.
In a pan, take some ghee and shallow fry half of the sliced onions till golden brown. Remove and keep aside.
In the same pan, fry the diced potatoes. Remove and keep aside. You can fry some cashews and kish mish if you like and keep aside.
In the same pan (add little more ghee if required) and fry the prawns for just a minute on each side. Do not over-cook them. Remove and keep aside.
In a big vessel/ kadhai/ handi take more than double the amount of rice you have take. Add the remaining whole spices with some salt and bring it to a boil.
Drain the water from the soaked rice and add them to this boiling water. Cook it till it is 3/4 cooked. Do not stir it repeatedly else the grain will break and the rice might become like a paste.
Drain/remove water from the rice and spread it on a plate to avoid any further sticking of the grains.
Now it is the time to assemble and prepare the actual Biryani.
In that same pan, take some more ghee add a bay leaf and add the remaining sliced onions to it. Fry them till soft.
Now add the ginger-garlic-spice paste to it and saute till the raw smell of garlic goes away.
Add chopped/sliced tomato to this, cover and let it cook for few minutes. Keep sauteing in between. Add turmeric powder, red chilly powder, cumin powder and coriander powder now.
As the tomato starts getting soft and saucy add curd and saute on high heat for a minute or so. Also add a pinch of sugar and some salt to this. Do not dry this masala mixture else you the biryani will end up very dry.
Reduce the flame and add the prawns and potatoes. Cover and cook for a minute and remove from flame.
In another pot/handi or pan (I have just used the same pan) add some ghee and spread the prawn mixture like a layer or a bed of prawn-potato curry.
On this add a mixture of chopped mint and coriander leaves (if you like more spice you can add finely chopped green chillies at this stage). Spread it all over the prawn layer.
Now add some of the fried onions and spread making another layer.
Now add the pre-cooked rice and make another layer of it.
You can repeat the layers again from prawn-potato then mint coriander then fried onions rice or have just one round of the layers.
Over the last layer, put the fried onions, mint-coriander leaves and fried cashews and raisins. If you want to add some more authenticity to this you can pour some saffron soaked in warm milk over the last layer.
In the end pour a teaspoon full of ghee over the rice. Cover it and cook / simmer for 5 to 6 minutes. Prawns do not need much cooking so do not try to cook it like any other meat biryani or you will be left with rubbery prawns.