Marinate the chicken with yoghurt, salt, red chilly powder, (clove elaichi cinnamon) powder, tej patta and little oil (2 tsp) for atleast 4-5 hrs .
Now in a kadhai, add refined oil. Deep fry the halved potatoes and keep aside.
Boil the basmati rice in water with rest of the whole garam masalas, salt till half done. Do not throw the starch hot water, will be used later.
Now in the same kadhai add the sliced onions and fry till golden brown, add the marinated chicken and stir.
Add the potatoes and cook till half done. Now add the the half cooked basmati rice, then sprinkle the fried onions, corriander leaves, saffron in milk.
Add ghee/refined oil (2 tbsp) to about half cup of the hot starchy water and spribkle this all over the layered rice. Sprinkle the Kewra water. Cover it and seal the lid of the kadhai with some dough. Cook on a low flame for 25-30 minutes.