Marinate the chicken with all the ingredients and keep aside for 1 hour. In a pressure cooker, add the butter and then the whole spices. Add the onions and sauté till pink. Then add the marinated chicken. Cook for 1 whistle or until chicken is tender. If the gravy is very watery then let it cook without the lid till it reduces.
Wash and soak rice for 20 mins before cooking. Cook the rice until almost done. Make a potpourri with all the spices and put it in the rice while it is boiling.
Heat the oven at 100 degrees. Take a Pyrex dish and smear it with butter. Make a layer of the cooked rice. Then spoon the chicken over the rice. Make another layer with the rice and top with the chicken in the centre. Dot the dish with butter and bake for 10 minutes at 150 degrees. Garnish the Baked Chicken Biryani with the egg slices and serve hot.
If you do not have an oven you can just layer the chicken and rice and serve.