Preheat the oven to 160 degrees Celsius.
Sterilise 3 x 250g jars by washing and rinsing thoroughly. Place the jars (after removing the rubber seal) on a flat baking tray and heat until all the water has evaporated.
Place 1 tsp rock salt in the bottom of each jar.
Wash, scrub and quarter 12 limes and thoroughly rub rock salt into the outer skins. Pack the lime quarters into the jars with the cardamom, kaffir lime leaves and peppercorns.
Juice the remaining limes and fill each jar to the top with lime juice.
Secure tightly and set aside in a cool place turning the jars each week for
4 weeks until they are ready to use.