Place tamarind in a small bowl. Cover with water. Leave to soak for 10 minutes. Drain. Discard hard bits. Set aside.
Ginger pickle:
Heat oil in a frying pan over medium-high heat. Add ginger. Sauté for 4-5 minutes or until ginger starts to change color. Add green chilies. Sauté, stirring, for 1 minute.
Add tamarind pulp, ground turmeric and red chili powder. Season with salt. Bring to boil. Reduce heat and simmer for 15 minutes or until raw smell of tamarind disappears.
Add jaggery and asafetida. Stir to combine. Simmer for 2 minutes. Remove from heat.
Tempered spices:
Heat oil in a frying pan over medium-high heat. Add mustard seeds. Allow to splutter. Add dried red chilies and curry leaves. Sauté, stirring, for a minute.
Add tempered spices to pickle. Cool completely. Store in an airtight container in the refrigerator for 4-5 days.