The most famous Bangladeshi version is kacchi biriyani, from the old part of Dhaka. The word 'kacchi' means 'raw' - because the meat and rice go into the pot raw at the same time, and cook together. The lid is sealed shut with a strip of dough, so no steam can escape, and the pot is left on a low fire for hours.
When the seal is finally cracked open at the table, the smell is unforgettable. Saffron, cardamom, cinnamon and rose water all rise up together. The rice is yellow and white and orange in patches. A small bowl of yoghurt with mint goes on the side, and a salty drink called borhani comes with it.
Biriyani came to Bangladesh hundreds of years ago, brought by cooks who travelled to the courts of the old kings of South Asia. Every region has its own version now: in Dhaka the rice is full of meat; in some places it is made with prawns, beef or just vegetables.
Sharing biriyani is a big deal in Bangladesh. When something happy happens - a baby is born, an exam is passed, a wedding is announced - friends and neighbours often get sent a parcel of biriyani in a foil container, so they can taste the good news too.