Real biryani is layered, not stirred. The cook first part-cooks long-grain rice with whole spices like cardamom, cinnamon and bay leaves. Separately, the meat or vegetables are cooked in a rich tomato-and-onion sauce. Then the rice goes on top of the sauce in layers, the lid goes on, and the whole pot is cooked very gently so the flavours rise up through the rice.
Different parts of Pakistan have their own biryani style. Karachi (in the south) is famous for a spicy 'Sindhi biryani' with green chilli and yoghurt. Lahore (in the east) likes a milder version with golden saffron rice. Children often eat a smaller, less spicy version with potatoes and chicken.
Biryani is served with raita - a cool yoghurt dip with cucumber, mint and tomato - which calms the spices on your tongue. On the side there are usually slices of lemon, fresh coriander, and little salted onions in pink vinegar.
The word biryani comes from an old Persian word, 'birinj', which simply means 'rice'. The dish has travelled all around South Asia, the Middle East and beyond. Almost every region now has its own version. But many people in Pakistan will tell you - with a friendly smile - that theirs is the best.