Dry roast all the ingredients in the Biryani Garam Masala section until aromatic. Grind the masala to a fine powder.
Marinate chicken with hung curd, ginger garlic paste, turmeric powder, red chili powder, lemon juice, Biryani garam masala, salt and oil. Leave the marinated chicken for 2 hours.
Fry Onion
Mix long sliced onion and rice flour. Heat oil in a frying pan and fry the long sliced onions at medium heat till golden color. Remove the fried onions and place it on a kitchen tissue towel.
Cooking Rice
Ingredient for cooking rice. Rinse the rice with water and soak in water for 30 minutes.
Add 10 cup water in a deep pan, add all the ingredients listed in for Rice section. You can adjust the salt to ensure the water is medium salty. Boil the water with all the ingredients at medium to high heat. Add rice in the boiling water, and cook the rice in a medium heat until it is 60% cooked. Drain all the water from the rice and keep it aside uncovered.
Final Prepration
Ingredient for final preparation. In warm milk, add saffron and kewra essence and keep it aside.
Heat oil in a pan then add cumin seeds, and bay leaves. Once the cumin seeds start crackles, add chopped onion, salt and saute it for 3 minutes or until onion becomes golden color at medium heat. Add diced tomato to the pan and cook it for about 3 minutes until tomato gets mushy.
Add marinated chicken, stir and cook with lid on at medium heat till the Chicken gets tender. Make sure to stir periodically so that it does not get burnt. Add Biryani masala and saute it for one minute, then turn off the heat.
In a slow cooker or heavy bottom pan, make a layer of cooked chicken, then add a layer of rice, spread mint leaves, coriander leaves, 2 tbsp ghee, milk with saffron and essence, and fried onion. Make one more layer similar to the previous one.
In a slow cooker cook for 30 minutes. If you are using a heavy bottom pan, cook it for 30 minutes at low heat. Add 1/4 cup heavy whipping cream on the top of the Biryani. Let it be covered for 15 minutes.