cooked together by baking, or medium-to-low direct heat (typically, for at least an hour). Cooking occurs by a process of steaming from the ingredients' own moisture: the cooking vessel's lid is sealed (traditionally, with a strip of wheat dough) so that steam cannot escape (proper dum pukht).A yoghurt-based marinade at the bottom of the cooking pot provides additional flavour and moisture. Potatoes often comprise the bottom layer (a technique also used in Iranian cuisine), because, with their natural moisture content, they brown well with less risk of getting burned accidentally. The lid is not opened until the dish is ready to serve. Kacchi biryani is technically much more demanding and time-consuming than pakki biryani, for the following reasons: The different ingredients—meat, rice, potatoes—have different cooking times: tender cuts of meat/chicken can be fully cooked well before the rice is done. To prevent this, many kacchi recipes use parboiled (semi-cooked) rice rather than raw rice. If direct heat is used, there is a risk that the food layer in contact with the vessel bottom may get burned while the interior's contents are still raw. This risk is minimized by sustained baking with moderate heat or very slow cooking on low direct heat. This approach, however, increases cooking time considerably. One method is cooking the dish "blind", with the cooking vessel sealed, so one cannot monitor the cooking progress—it takes the understanding of the raw foods used, the heat required to cook those raw foods, and how the climate can affect the cooking process. Hence making kacchi biryani requires a seasoned hand. Varieties In the Indian subcontinent There are many types of biryani, whose names are often based on their region of origin. For example, Sindhi biryani developed in the Sindh region of what is now Pakistan, and Hyderabadi biryani developed in the city of Hyderabad in South India. Some have taken the name of the shop that sells it, for example: Haji Biriyani, Haji Nanna Biriyani in Old Dhaka, Fakhruddin Biriyani in Dhaka, Students biryani in Karachi, Lucky biryani in Bandra, Mumbai and Baghdadi biryani in Colaba, Mumbai. Biryanis are often specific to the Muslim communities where they originate; they are usually the defining dishes of those communities. Ambur/Vaniyambadi biryani Ambur/Vaniyambadi biryani is a variety cooked in the neighboring towns of Ambur and Vaniyambadi in the Tirupattur district of the northeastern part of Tamil Nadu, which has a high Muslim population.