Lassi is the classic yogurt drink of the Indian subcontinent — dahi (curd) whisked or blended with water and either salt and spice or sugar and fruit until thick, cool and frothy. Its tangy lactic body, gentle acidity and cooling creaminess make it the everyday partner to fiery Punjabi and North Indian food; the two great forms are salty lassi, seasoned with roasted cumin and a pinch of salt, and sweet lassi, sweetened and perfumed with cardamom, rosewater or saffron, of which the fruit-blended mango lassi is the best-known abroad.