Using a sharp knife, cut each lime in half. Then cut the halves into quarters for a total of 8 wedges per lime.
Place the wedges into a medium bowl and sprinkle the salt on top.
Sprinkle with the salt. Then cover a place and set in a cool, dry place to ferment for about 2 days.
Have all the remaining ingredients ready along with sterilized glass jars (see note).
Place a medium skillet over medium heat and add the oil. Once it’s shimmering hot, add the mustard seeds and wait until they start popping. Add the garlic, ginger, cumin, coriander and chilli powder and stir for 30-60 seconds until fragrant.
Add the lime pickle mixture, water, vinegar and brown sugar to the pan. Bring to a boil and reduce heat to low. Simmer for 10-15 minutes or until the sauce has thickened slightly.
Spoon the mixture into the prepared glass jars. Seal and invert for several minutes. Then set aside for one week to allow the flavor to develop before serving.