Soak the tamarind ball in hot water for 30 minutes. Mash it well and strain to extract the pulp. Set aside.
Sauté the ginger:
Heat 1 tsp oil in a kadai (deep pan) over medium heat. Add the sliced ginger and sauté for 3-5 minutes until it turns light golden. Remove from heat and let it cool.
Roast the spices:
In the same kadai, dry roast the urad dal, chana dal, green chillies, cumin seeds, coriander seeds, and fenugreek seeds for 3-4 minutes on low heat until fragrant. Set aside to cool.
Grind The Chutney:
In a blender, combine the sautéed ginger, roasted spices, tamarind pulp, jaggery, and salt. Grind to a fine paste, adding water as needed to achieve the desired consistency.
Prepare the tempering:
Heat 1 tsp oil in a small pan. Add mustard seeds and let them splutter. Add urad dal, cumin seeds, curry leaves, and red chillies. Fry until the dal turns golden and the curry leaves become crisp.
Finish the chutney:
Transfer the ground chutney to a serving bowl. Pour the tempering over the chutney and mix well.
Serving and Storage
Serve the Ginger Chutney with pesarattu, idli, or dosa. Store any leftover chutney in an airtight container in the refrigerator for up to a week.