Marinate the mutton with the ingredients mentioned in marination list for atleast 30 minutes.
In a heavy bottom pot or pan heat the oil.
Add 1 thinly sliced onion and fry till golden. Your fried onion is ready. Set aside in a plate.
In the same pan add in the cashews and fry until golden. Remove and keep aside. Add in the raisins and fry the raisins for few seconds. Remove and keep aside along with the fried cashew nuts.
In the same pot add in the ghee. Add bay leaves, cinnamon stick, cloves, cardamom, star anise and let it crackle
Add in ginger garlic paste and saute for a minute.
Add in the green chillies, remaining onions and saute until the onion starts to brown.
Add in the tomatoes and fry until it turns soft and mushy.
Add in the marinated mutton and mix well. Cover the pot and cook over high flame for about 5 to 10 minutes or until the water released from the mutton evaporates completely. Stir occasionally in between
Add in some water. Cover the pot and cook further for few minutes. Add in coriander leaves and mint leaves.
Put on the lid and cook further until the mutton is cooked completely and ttender. Keep the consistency as thick masala gravy.
Meanwhile wash the rice nicely and soak it for 15-20 minutes.
In a pot bring water to boil for cooking the rice. Add in the oil, whole spices, coriandee and mint leaves.
When the water starts to boil add in the drained soaked basmati rice.
Cook the rice only till 70% cooked approximately 5-7 minutes. Drain the rice nicely and keep aside.
Once the mutton is done start layering the mutton and rice for dum. I used the same pot where I cooked mutton. Keep some mutton pieces and masala and over it layer some portion of rice.
Sprinkle some fried cashew nuts and raisins. Continue the layering process of rice and mutton.
Finally sprinkle coriander leaves, mint leaves, fried cashew nut, fried raisin and fried onions.
Sprinkle the saffron milk all over on top. Cover the pot with lid. Place a tawa (griddle) over low flame. Place the biryani pot over the tawa for dum.
Let it cook on dum for about 15-20 minutes. Your mutton dum biryani is ready.
Remove from the flame, open the pan and fluff it gently with a fork gently. Serve it with salad and raita of your choice.