Check the salmon for bones and remove with tweezers.
Line a dish or roasting-tray, large enough to hold the salmon, with a double layer of foil.
Put one of the pieces of salmon, skin-side down, on top. Rub it all over with half the whisky.
Mix the sugar, salt, pepper, dill and apple and spread it over the salmon.
Pour on the rest of the whisky and put the other piece of salmon, skin-side up, on top.
Pull the foil up around the fish, then place a heavy board on top. Place into the refrigerator for two to three days, turning the fish over every so often.
Pour off any liquid that seeps out.