Wash the rice and soak in water for 30 minutes.
Drain the rice and add 1 tsp ghee to it and mix well and allow to marinate for 20 to 25 minutes.
Cut the mushrooms in half and keep aside.
Grind chopped mint leaves, chopped coriander leaves, green chilies, garlic & ginger to a fine paste. You can add a little water to grind the paste.
In a mixing bowl combine curd turmeric powder, red chili powder, garam masala powder coriander powder and salt.
To this add the ground masala paste and mix well.
Add the mushrooms and mix so that the mushrooms are evenly coated with the masala. Cover and keep aside to marinate for 30 to 40 minutes.
Heat oil in a pan and fry the all the whole garam masala.
Add sliced onions and sauté for 4-5 minutes till the onions turn pink and translucent
Add chopped tomato and green chilies.
Add the marinated mushrooms and sauté for 6 to 7 minutes or till they shrink and you see the oil separating from the masala.
The mushrooms will release water as they shrink.
Now add the rice and mix well.
Add coconut milk, water and salt and mix well.
Cover the pan and cook on a low flame for 15-18 minutes or till the rice has cooked.
Uncover and allow the biryani to stand for 5 minutes before serving.
Serve Chettinad Mushroom Biryani with onion raita and papad.