Soak the lemons for 2 days before preparing this recipe. Change the water twice.
Remove the nut end of the lemon (the end that attaches the lemon to the tree). Slice a cross two-thirds of the way up the lemon. Fill with rock salt, don't be shy. Place into glass jar. Repeat this process until there are enough lemons compacted into the glass jar. Make sure there is enough room (about 1/4 of the jar) left at the top to accommodate any excess juices from the lemons. Secure tightly with the lid and place in a cool dark place for at least a month.
Some people add 1/2 cup of fresh water to encourage the process of preservation, with the addition of olive oil to act as a sealant on top of the lemons. These last two processes are not necessary. Some people also add cinnamon sticks and cloves or black peppercorns, it entirely depends on your individual taste. Simple is best.
The lemons will then be preserved and ready to use. They last for about 4 years.
Remember not to use a jar with a metal lid as this will affect the preserving process and the metal may erode.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.
Recipe courtesy of Ben O'Donoghue, Montes, London