Cut ginger into pieces of .5 cm.Cut green chillies into fine pieces. To 1 cup of ginger pieces, add 2 tsp of chillie pieces, 3/4 tsp salt. Squezze out 1 small lime onto the mixture. Heat 1 tsp of oil and add mstard seeds. When they pop, add it to the mixture. Leave it for about 30 min. Store in refrigerator.