This biryani is based on the many seafood biryanis of the Malabar coast. These are often simple and delicious and mostly garnished with local cashew nuts and raisins. Here we have also added the more elegant saffron-milk and crispy fried onions but do leave them out if you prefer, the dish is still delicious without. You can make these at home by frying thin slices in hot oil until golden and crisp on the edges or buy them ready made (albeit in smaller broken pieces) and sprinkle over a handful. The butter is also optional for when it is a special occasion, leave out if you prefer.