Chop the ginger in to very small pieces and small onions in to thin round pieces. Cut the green chillis in to small round pieces. Fry the ginger in a kadai (pan) using enough oil. After it gets brown, remove it from kadai and grind the ginger without using water. Season it by frying mustard seeds and sliced small onions, followed by curry leaves and green chillies. Add the prepared ginger, chilli powder and mix it well for 1 minute. Add tamarind pulp, a little bit of water and salt. Keep the mixture in low fire for 3-4 minutes.
You can add Jaggery, or sugar in to the curry for a little sweetness.