This method of cooking mackerel has been tested by me more than once. And believe my experience, it is no worse than in a supermarket. Even there is a plus - it is much fresher.
We take three mackerels of medium size.
If it is frozen, then you need to defrost. Then cut off the heads, tails and fins. Cut the abdomen and remove all the insides. Rinse well and set aside for now.
Pour 1-2 liters of water into the pan and bring to a boil. Then we take onion peel from about 3 onions and lower it into water.
We close the lid and boil for about another 25 to 30 minutes on reduced heat. Then remove from heat and let cool completely. When the water has cooled, filter it. Husk we no longer need. We continue to prepare the brine. In filtered water, add 1-2 tablespoons of sugar, 3 - 4 tablespoons of large salt and 1 tablespoon of liquid smoke. No more pouring, one is enough. Now mix everything thoroughly.
We need dishes that are covered with a lid. We put the fish there and fill it with brine.
Now you need to put it in the refrigerator for a day. If you make fish in the winter, you can leave it on the balcony. After 24 hours, we take out the fish and turn it over to another barrel. Then put in the refrigerator for another day. Then we proceed to the final stage of preparation. We take the fish out of the refrigerator. With an awl we make a hole in the carcass about 2 centimeters from the tail. This is necessary in order to put the hook in there and hang it on the balcony.
It should dry for 1 day and preferably in the shade. And in the end, we only need to grease it with sunflower oil. That's all.