Gravlax is raw salmon, usually cured in a mixture of salt, sugar and alcohol. I use vodka, but other approaches call for more powerful spirits such as cognac or bourbon. This treatment, Scandinavian in origin, resembles the curing or smoking methods of preparing fish in Britain or Eastern Europe — though there is no smoke used here. It can be made using a whole fish, but at home you’re probably better off with just two substantial fillets. It is usually sliced very thinly on the bias (a sharp slicing knife is essential) to reveal as much of the surface of the flesh as possible. While this is a very simple recipe, the curing takes three days, so plan ahead.