1. Scrape and wash the ginger thoroughly, and cut into thin slivers (about 1 cup). Put these into a bowl.
2. Wash, wipe and cut the chillies into 2-3 pieces each.
3. Heat the oil, add the mustard and when done, add the green chillies and saute for one to two minutes or till they turn soft. Transfer this to the bowl.
4. Extract the juice of the lemons, add salt and mix this along with the ginger and chillies, and transfer to a bottle. Refrigerated, it will keep for one to two weeks.