Chop the ginger, garlic and lemongrass and place in a mortar. Add the chillies and half of the lime rind, keeping the other half aside for later. Crush the ingredients together in the mortar. Gradually add the vinegar. Add a pinch of salt and continue pounding. The salt will assist breaking down the other ingredients. Taste the mix to ensure you are happy with the combination of sweet, sour, salty and hot flavours. Add additional amounts of the ingredients as required to balance the taste to your liking. Add the mix to a cold pan. Place the pan over high heat. Be careful not to let the flame come up around the sides of the pan this will burn the edges. Mix the sambal with a wooden spoon as it heats. Add the sugar. This will caramelise the mix and bring the flavours together. Cook over medium heat for 10 minutes or until the mixture is pulpy. When the mix is almost done, add the remaining lime rind. Cook for a further 90 seconds. Serve the sambal hot or cold, as an accompaniment to just about any dish.