Curing and preserving mackerel is a long-standing tradition in the Oslo Fjord region. I use rapeseed oil in this recipe and I allow the Kilner jar to stand in a pan of boiling water for a few minutes before putting the lid on.
For one large Kilner jar (0.5 gallon).
Sterilize the Kilner jar in the pan of water in the oven.
Clean and wash the mackerel and cut it up into 1.2 – 2 in. thick slices. Sprinkle the salt evenly over the pieces of fish. Place the fish in the Kilner jar, interspersed with the bay leaves, the coarsely chopped herbs and the sliced celery.
Put a saucepan, which is almost as tall as the Kilner jar, on a hot plate and place the Kilner jar inside it. Heat up the oil to 185 – 203oF and carefully pour the hot oil over the fish. Then pour the boiling water into the saucepan to create a water bath. Place it on the hot plate and let the water boil for five minutes. Use a new seal for the Kilner jar and secure the lid. Cool, and then tighten the lid.
Using this method you can store the fish for several weeks, preferably in a cellar or in the fridge.