In a large pot for biryani take water, bay leaf, cumin, black pepper and salt. Bring water to boil then add soaked rice. Mix well so spices release flavors. Cook rice until 70% cooked then drain all water and keep rice in strainer until required. (Mix little oil in rice to avoid sticking.)
In a wok, fry potatoes with a pinch of salt until golden brown, transfer potatoes to paper towel and set aside.
In same wok, leave only ½ cup oil and (remove extra oil ) cook marinated chicken for 7 minutes until color changes then add tomato puree and cook further for 10-15 until all tomato water dries and oil separates. Your chicken should be tender by now or cook further as needed. Sear chicken ( bhunofy) well for rich taste.
Now add whipped yogurt,and bring gravy to a boil. Now, mix in chat masala (if using) potato, prunes, mint, coriander and green chilles, mix well. Chicken gravy is ready.
In the large thick bottom rice pot smear 2 tablespoon oil in bottom.
Mix orange color, saffron and water together. Spread evenly over the rice. ( You may also add kewra water along with saffron)
Cover pot with foil to seal the steam. Cover with lid too. Keep the pot for dum for 15-20 minutes until rice are fully cooked and steam rises to the top when lid is removed.
Mix rice with a large flat spoon or a small plate. (Do not over mix to break grains.) And serve hot with raita and kachumber.
Rice are most important thing in biryani. Boil rice should be aromatic with spices. Make sure your are under-cooked when you boil because we'll cook again for 20 minutes.
Searing ( bhunofying) is most important step in making gravy.The yogurt you add later with restore water content of gravy but if your gravy is too dry add little extra water.