Curing fresh salmon enhances its taste and transforms its texture, writes Emma Knowles.
Gravlax. Gravad laks. Gravad lax. Graflax. There are many ways to spell and pronounce it, but all describe the Nordic dish of cured raw salmon. The name translates from the Swedish as "buried salmon" - "grav" means grave, and "lax", salmon - referring to the old custom of salting salmon and other freshly caught fish and burying them in a barrel or in the ground above the high-tide line. The fish would be enjoyed after a few days of curing, or left to ferment for several months, preserving it for the leaner months when food was scarce.
At its simplest, the cure consists of a combination of salt, sugar and dill, although in its earliest incarnation the aromatic flavour was imparted by pine needles. More modern additions include lemon rind, dill seeds, juniper and sometimes a splash of booze - either vodka or gin.
Making gravlax isn't difficult, but it's not for those who seek instant gratification. You'll need to plan ahead to allow for the curing time.
Ultra-fresh salmon is absolutely imperative for making gravlax (or any other cured fish, for that matter), both for reasons of food safety and to ensure the best taste and texture. The best way to ensure freshness is to visit a large fish market or a fishmonger you know has a high turnover. Ask your fishmonger to cut you a fresh side of salmon, rather than relying on pre-cut fish that may have been sitting there for a day or two. Many fishmongers will remove the pin-bones while they're at it - these are the "floating" bones not attached to the skeleton of the fish. But if not, it's a simple task to remove them yourself. Fish tweezers, which are available from specialist cookware shops, have a square, blunt end that makes it easy to grasp the pin-bones and remove them without damaging the flesh.
Trim the fillet to create a rectangle of salmon of more-or-less even thickness, which allows it to cure evenly: trim the belly a little and remove the tail. If you were to leave these thinner parts of the fish on, they would over-cure and be chewy and unpleasant to eat. (These trimmings needn't go to waste - they're perfect for a salmon tartare.)
Next, the curing process. The salt in the cure acts in three ways. First, it inhibits bacterial growth and extends the stability and shelf-life of the salmon. Second, it draws moisture from the salmon through osmosis, creating a dense texture. And third, it tenderises the fish by breaking down the protein structure. The sugar ensures the gravlax isn't too salty, while fresh dill, dill seeds and lemon rind contribute fragrance and flavour.
It's important that the curing mixture is in contact with all surfaces of the fish so it cures evenly. Wrapping and weighting the salmon helps to spread the cure, press it into contact with the flesh, and remove air pockets. Use several layers of plastic wrap to minimise leakage, and place the fish parcel on a tray. As the curing progresses, the salt mixture will dissolve and liquefy, and the tray will catch any juices that escape the plastic wrap. The traditional method of weighting involved bark and rocks, but these days a board and some food cans will do the job.
Refrigerate the salmon for two days for a light cure, or up to a week for a stronger cure, which will result in a more intense flavour and a denser texture. Turn the fish parcel every 12 hours or so, so that the cure continues to spread. When the fish is cured to your liking, brush away the cure, wipe off any moisture and wrap the fish in fresh plastic wrap. It will keep for four to five days from this point.