Cut the limes into quarters, salt and keep, covered for 3-4 days. Grind together the chillies, turmeric, cummin and mustard. Peel the garlic but keep cloves whole. Slice the ginger. Heat the oil in a large pan. Add the garlic, ginger and curry leaves and cook until the garlic has browned slightly. Add the ground spices and chopped green chillies. Cook for a minute or so and then add the vinegar. Wash the limes in a little vinegar and add to the pan along with the sugar. Bring to the boil and cook for 15-20 minutes over a low heat. Cool and bottle. Eat after 3-4 weeks.
