Drain the soaked urad dal completely. Grind in a mixer with minimal water (2-3 tablespoons) until thick and fluffy. The batter should hold its shape when dropped.

Transfer to a bowl and whip vigorously with a spoon for 3 minutes to incorporate air. Add chopped green chilies, ginger, curry leaves, asafoetida, and salt. Mix well.

Heat oil in a kadhai on medium heat. Wet your hands, take a small portion of batter, shape into a ball, flatten slightly, and make a hole in the center with your thumb.

Slide the vada gently into hot oil. Fry 3-4 vadas at a time until golden brown on both sides, about 4 minutes total. Drain on paper towels.

Once all vadas are fried, soak them in a bowl of warm water for 2 minutes, then gently squeeze out excess water. Set aside.

Pressure cook toor dal with 2 cups water and turmeric powder for 4 whistles or until completely soft. Mash well and set aside.

In a separate pot, add chopped vegetables with 1 cup water and cook until tender, about 8 minutes.

Squeeze the tamarind in warm water and extract the pulp. Strain and discard the solids.

Add the cooked dal to the vegetables. Pour in tamarind extract, sambar powder, jaggery, and salt. Add 1-2 cups water for desired consistency.

Bring to a boil, then simmer for 10 minutes until flavors blend and the raw tamarind smell disappears.

Heat oil or ghee in a small tadka pan. Add mustard seeds and let them splutter. Add cumin seeds, dried red chilies, asafoetida, and curry leaves. Fry for 20 seconds until aromatic.

Pour the tempering into the sambar and mix well. Simmer for another 2 minutes.

Just before serving, gently place the soaked vadas into the hot sambar. Let them sit for 5-8 minutes to absorb the flavors.

Garnish with fresh coriander leaves and serve immediately.