Wash the mutton and mix it well with curd, green chilli paste, ginger garlic paste, golden fried onion, coriander powder, turmeric powder, red chilli powder, garam masala powder, cumin powder, salt and lemon juice.
Marinate the mutton for at least 2 hours or overnight.
Heat oil in a pressure cooker.
Add onion and fry until onion turns golden brown.
Add the marinated mutton and fry on high heat for 4-5 minutes.
Now add 1 cup of water and pressure cook until mutton is tender.
Remove the lid of the cooker and cook the mutton until most of the water is evaporated.
Add coriander and mint and mix well. Keep the mutton aside.
For the rice
Wash the rice and soak in water for 40-45 minutes.
Heat water in a large pot.
Add potli masala, ghee, salt, ginger garlic paste, green chilli paste, kewra essence and shahi zeera in the pot and bring the water to a boil.
Cook the rice until it is 90% cooked.
Drain the rice and keep aside.
Assembling the biryani
Transfer the cooked mutton in a heavy bottom pan.
Drain the rice and layer it over the mutton evenly.
Sprinkle 1/4 cup milk, saffron soaked in water, golden brown onion and ghee on top.
Cover the pan tightly with a lid.
Place the pan on a very slow heat for 20-25 minutes.
Remove the lid and mix the biryani gently.
Use best quality rice to make biryani.Keeping a heavy tawa below the pan helps to cook the biryani on very low heat and it also makes sure the biryani doesn't get burned from the bottom.The traditional potli masala used to make biryani recipe has many unusual ingredients, but since it is not easy to source them, I have a mix which is easy to find the not compromise on taste. To make potli masala, tie 2 g green cardamom, 2 g cloves, 2 g bay leaves, 2 g cinnamon and 2 g star anise in a small cloth pieceBirista or Golden Fried Onions are a must to make a good biryani. Making perfect birista is an art and takes a lot of patience and skills. I have a detailed recipe to make perfect birista at home. You can check the recipe to make golden fried onion here. Be very attentive while cooking the rice. Do not stir the rice much while cooking otherwise it will break the grains.Choose a pan with a tight fitting lid. This biryani cooks on dum or steam and we want to retain as much steam that is formed inside. Traditionally, a sealing of dough used to be put around the pan and the lid but I don't think that it is required if the lid fits tightly.