Heat oil in a pan on medium heat and add mustard seeds. Once that cracks, add grated ginger and saute till ginger cooks well.
Add green chillies + curry leaves + chilly powder + salt + turmeric powder and mix well for an additional minute.
Squeeze tamarind pulp into water and add that water. Once that simmers, add grated or crushed jaggery and let the mixture simmer again on low heat. Adjust salt, jaggery or tamarind as per taste if necessary.
Turn off the heat once the chutney thickens and a layer of oil is visible.
This stays well in the refrigerator for few weeks. Can be used as a spicy dip or as a side with rice.