Place the chicken pieces in a bowl, mix in the ingredients for the marinade, cover and refrigerate for at least 3 hours and upto 8 hours.
Wash and soak the Basmati rice for 20 minutes. Drain completely.
While the rice soaks, heat 1½ tbsps of ghee in a wide, heavy-bottomed pan / pot, add half the sliced onions and fry till translucent.
Add the chicken and half the curry leaves and fry (bhuno) the chicken pieces on a medium flame. Put in the grated mango and cook the chicken for a further 10-12 minutes till the chicken is half cooked, the mango soft and pulpy and you have a thick gravy coating the chicken.
Take the chicken out of the pan, add the remaining ghee and add the whole spices. Fry for 10 secs and add the rest of the onion.
Fry till the onions are golden and then put in the soaked and drained rice. Fry the rice on a low flame for about 5 minutes till it is toasty and coated with ghee.
Put in the chicken and the remaining curry leaves. Gently mix with the rice, spread the pulao in an even layer on the pan and add enough water to just cover the chicken and rice (only ½ mm above the surface, too much water will make the pulao mushy).
Cover the pan with a tight-fitting lid and cook on a low flame for 20 minutes.
After 20 minutes, take the covered pan off the heat and allow it to rest for 15 minutes before opening. Gently lift the chicken and rice with a flat serving spoon into a serving dish and serve with cucumber raita.