Step 1 - Put the limes into a large bowl and sprinkle with the salt and leave to soak in for 24 hours.
Step 2 - Next day put a preserving jar (lid and glass separate) into the over for 10 minutes at 150 degrees.
Step 3 - Next day put the mustard seeds, fenugreek, star anise seeds and chillies into a saucepan and cover. Place this on a high heat and stir constantly until the mustard seeds start to pop. Remove from the heat and place in a bowl.
Step 4 - Strain the liquid from the limes and add to the pan that the spices were roasted in. Add the sugar, ginger and water. Boil for two minutes until the sugar has dissolved.
Step 5 - Combine the limes, spices and liquid and then spoon into the warm jar (the limes should be completely covered with the liquid) and loosely put the lid on. When the jar has almost cooled completely, screw the lid on tightly.
Step 6 - Keep in a cool place for four weeks before opening.