Wash and soak 250 grams of urad dal in water for 4-5 hours or overnight.
Drain the water and grind the soaked urad dal into a smooth, thick batter using a little water if needed. The batter should be of dropping consistency.
Add 1 finely chopped green chili, 1 teaspoon of grated ginger, 1 tablespoon of finely chopped curry leaves, 1 tablespoon of chopped coriander leaves, and salt to taste. Mix well.
Heat oil in a deep frying pan or kadai over medium heat.
Wet your hands, take a small portion of the batter, and shape it into a round disc with a hole in the center, like a doughnut.
Gently slide the shaped vada into the hot oil and fry until it turns golden brown on both sides. Fry 2-3 vadas at a time, depending on the size of your kadai.
Remove the fried vadas from the oil using a slotted spoon and place them on a paper towel to absorb excess oil.
Serve hot with coconut chutney and sambar.