Marinate the Chicken: Combine the chicken with all marinade ingredients in a large bowl. Mix well, cover, and refrigerate for at least 1 hour — overnight is even better.
Parboil the Basmati Rice: Bring a large pot of water to a rolling boil with the salt and whole spices. Add the drained rice and cook for exactly 5-6 minutes, until the grains are about 70% cooked. Drain immediately.
Cook the Chicken Masala: Heat 3 tbsp oil or ghee in a heavy-bottomed pot. Add the marinated chicken and cook on medium-high for 5 minutes to seal, then cover and cook on medium-low for 12-15 minutes until the chicken is nearly done.
Layer the Biryani: Over the chicken, layer half the parboiled rice, half the fried onions, mint, coriander, and saffron milk. Repeat with remaining rice and toppings. Drizzle ghee over the top and tuck in green chilies.
The Dum Cooking: Cover with a tight lid and seal the rim. Cook on high heat for 3-4 minutes, then reduce to the lowest flame for 20-25 minutes. Rest covered for 10 minutes. Fluff with a fork and serve.