Rinse the basmati rice thoroughly and soak for 20 minutes. Drain and set aside.

Heat a tablespoon of oil in a large pot over medium heat. Add sliced onions and sauté until golden brown.

Add the ginger-garlic paste, green chilies, and chopped tomatoes. Cook until the tomatoes are soft.

Stir in the spices: turmeric, garam masala, coriander, cumin, and masala. Cook for 2-3 minutes.

Add the sliced mushrooms and cook until they are soft and lightly browned.

In a separate pot, bring water to a boil. Add the soaked basmati rice, salt, and whole spices (cardamom, cloves, cinnamon). Cook until the rice is 70% done, then drain.

Layer the cooked mushrooms in the bottom of the pot, and spread the parboiled rice over the top. Sprinkle with saffron milk and fried onions.

Cover the pot with a tight lid and cook on low heat (dum) for 15-20 minutes until the rice is fully cooked.

Fluff the biryani gently and serve hot with raita or naan.