Marinate the Chicken: Whisk yogurt, ginger garlic paste, lemon juice, spices, chilies, salt, and oil; coat chicken with mint and coriander; refrigerate at least 1 hour or overnight (up to 24 hours).
Soak the Rice and Fry the Onions: Rinse and soak basmati 30 minutes. Fry sliced onions in batches in ½ cup oil until deep golden and crisp; drain and salt lightly.
Parboil the Rice (70% Rule): Boil rice 5–6 minutes in salted water with bay, cardamom, cloves, cinnamon, and cumin seeds until exactly 70% cooked (firm with a chalky center); drain immediately.
Layer the Biryani: Grease pot with 1 tablespoon ghee; layer marinated chicken, half the rice, half the onions/herbs/saffron milk; repeat; drizzle remaining 2 tablespoons ghee on top.
Cook on Dum: Seal pot with foil and lid; high heat 4–5 minutes until steam escapes, then lowest heat (on a tawa) for 25 minutes undisturbed. Do not open the lid.
Rest and Serve: Rest sealed 10 minutes off heat; check chicken is 165°F / 74°C; fold gently and serve hot.