Wash and soak basmati rice for 30 mins. Drain and set aside.
Keep a pot full of water and bring it to boil, add the whole garam masala required for making the rice and add the rice when the water comes to boil.
Once the rice is cooked to al dente, remove it and let it rest for some time, meanwhile, we can make the mushroom gravy.
For Making Mushroom Gravy
Heat oil in a pot/wok, add whole spices/garam masala and let it sizzle, add in onions and cook till golden, add ginger garlic paste and mix well and add chopped green chillies and sauté it for some time.
Add tomatoes and cook till mushy, add salt, spice powders and mix well. Add brown onions, the coriander and mint leaves and let them cook for some time. Now we can add the Almond and Cashew paste and cook further till the whole mixture starts leaving oil in the corners. add in mushroom and cook well.
Once the gravy is ready keep it aside.
Final Part: Layering Rice and Mushroom Gravy
In a pot first, add basmati rice layer at the bottom and then the mushroom gravy layer and then the rice. Take care that the last layer should be rice and sprinkle coriander leaves, mint and brown onions. Close the vessel and let it simmer for a while till the rice is cooked properly.
Turn off the heat and let it rest for some time and serve it with raita or papad.
I have used an electric cooker to get the last part of steaming to be done.
Brown onions are finely chopped onions deep fried till they are crisp and brown. Brown onions enhance the taste of the biryani.
Do not wash the mushrooms, wipe them and cut them into four quarters and use it for preparing the gravy.
Mushrooms do not require too much of sautéing.
Brown onions, Coriander and Mint leaves have mentioned in two quantities one is for the gravy and the other lot is for using it to sprinkle at the last.