Wash and soak the black lentils in 4 cups water for 2 hours.
Drain all the water and grind to a smooth paste using very little water. Add salt while grinding. The batter should be thick.
Add coriander leaves, green chillies, ginger, rice flour and mix well.
Heat oil in a deep bottomed pan on a medium flame. Wet your palm and take a lemon sized batter.
Gently pat the batter and make hole in the center.
Gently slide shaped batter into the hot oil. Make sure that the oil is not too hot. Otherwise the vada will not cook evenly.
Fry on both sides till it becomes golden brown color.
Serve hot with chutney and sambar, or pickle.