Whiskey (yes, whiskey!) - 10% of the weight of the fish
A generous handful of dill, even dried.
Cut the fillet into two pieces. Dissolve salt in whiskey.
Pour insoluble salt residues between two pieces of fish, put them in a sandwich with scales outward, sprinkle with dill on top. Put the sandwich in a small deep form.
Fill the fish with a mixture of whiskey and salt: it is important that the liquid level is not lower than 3-5 mm from the top edge of the fish. That's why a small and deep form is needed.
Tighten the mold with foil and refrigerate for 48 hours. If after the first 24 hours the liquid level remains below the top edge of the fish, turn the sandwich so that the top edge of the fish is immersed in the marinade.
Drain all the liquid and cut the fillet into translucent pieces with a help of a loin knife.