Soak 1 cup urad dal in water for 4 to 6 hours
Drain the water completely
Grind the dal to a smooth, thick batter using very little water
Add salt to taste and whisk the batter well until light and fluffy
Heat oil for deep frying
Drop small portions of batter into the hot oil
Fry the vadas on medium heat until golden brown
Remove and drain excess oil
Soak the fried vadas in warm water for 10 to 15 minutes
Squeeze out the excess water gently
Whisk thick curd with salt and a little sugar
Place the vadas in a serving dish
Pour the whisked curd over the vadas
Add tamarind chutney and green chutney
Sprinkle roasted cumin powder, red chili powder, and chaat masala
Garnish with coriander leaves and sev if desired
Serve chilled