You start off with a tail piece of salmon, weighing approximately 1 kg. Get your fishmonger to slice it in half, lengthways, and to remove the backbone, so that you end up with two slices of fish. Remove the remaining 'pin bones' with a pair of tweezers. Gravlax is usually made with the skin of the fish left on, but if you prefer, you can remove it.
Next, you need to mix up 'The Cure". Combine the following ingredients in a bowl: one heaped tablespoon of sea salt, one tablespoon of brown sugar, one teaspoon of crushed black peppercorns, and one tablespoon of cognac, schnapps or vodka.
Take some tin foil, and lie it down, flat. Spread some of the cure onto the foil. Lie one of the salmon pieces down onto the foil. Spread more of the cure onto the upper side of the salmon. Next, sprinkle lots of fresh, chopped dill on top of the salmon. Take the second piece of salmon, spread it with the cure, and place it directly on top of the first piece of salmon, so that you end up with a sort of salmon sandwich, with the dill and cure mixture filling up the middle. Does that make sense?
Fold over the tin foil, and crunch it tightly around the salmon pieces, so that it forms a package. Lie this in a shallow dish, and press some weights down on top of it. I use some heavy iron weights from my grandmother's old-fashioned scales I've got lying around in my kitchen. Keep the salmon in a cool place for up to five days, turning the fish over once or twice. You'll find that juices from the fish will run out and mix with the cure and the dill. In effect, you're curing the salmon.
You make Dill Sauce in a similar way to mayonnaise. Crack an egg yolk into a bowl, and mix in a dollop of French Dijon mustard and a tablespoon of white sugar. Whisk, and start to add Grapeseed Oil, drop by drop- as you would with a mayonnaise. The emulsion will thicken. Keep going until you're happy with the consistency. I like it thick. Flavour the sauce with two tablespoons of white wine vinegar, and season with salt and pepper. Finish it off by mixing in a decent amount of fresh, chopped dill. It's best if you remove the dill stalks, and then chop the feathery bits of the dill plant finely.