Marinate the chicken with ginger-garlic paste, red chili powder, turmeric powder, garam masala, salt, and cornflour. Set aside for 30 minutes.
Heat oil in a frying pan and fry the marinated chicken pieces until golden brown. Set aside.
In a large pot, cook the soaked basmati rice until 70% done. Drain and set aside.
In the same pot, heat ghee and sauté sliced onions until golden brown. Add chopped tomatoes and cook until soft.
Add yogurt, red chili powder, turmeric powder, garam masala, and salt. Cook until oil separates.
Add the fried chicken pieces and mix well. Layer the partially cooked rice on top of the chicken mixture.
Sprinkle chopped coriander leaves, mint leaves, and saffron milk over the rice. Cover and cook on low heat for 20-25 minutes.
Fluff the biryani gently and serve hot.