the sweetness is a pleasant contrast to the zingy marinade, but I have to concede that it's probably not an essential. It is, however, absolutely vital to use a generous amount of citrus -- that way you get a good spoonful along with the fish. Peruvians often drink the leftover marinade, known as tiger's milk, after finishing the dish itself, but this is strictly optional -- as a hangover cure, it's in the do or die category. Alliums Alliums of some sort are almost non-negotiable: Aikens and olive use finely chopped shallots while everyone else goes for red onion. I prefer the more straightforward sweetness of the latter, but I think soaking it in iced water briefly before use, like Morales, is essential if it isn't to overpower the entire dish. It seems more usual to leave the onion in thin strips, but I'm going to finely dice it so every bite of ceviche has a good balance of flavour. Spices and other ingredients The Last Days of Pisco recipe ceviche. Photograph: Felicity Cloake Everyone apart from Aikens uses chilli, but the only recipe I find calling for the aji amarillo , a fruity pepper described by Henrietta as having a citrussy, almost pineapple-like flavour and popular in Peruvian cooking, is her own. They're difficult to track down in this country, but you can order them dried online, or find them frozen in South American shops -- I reconstitute a dried chilli, and pound it into a paste for Henrietta's