wash and soak dal in about 3 cups of water for about 2-3 hours.
drain all the water from soaked dal. grind urad dal and channa dal together to smooth paste using very little water. i have used authentic grinding stone, but wet grinder or even mixer grinder can be used.
the batter should be thick and use very little water. the right consistency is very important or otherwise, you will not be able to get the vada shape.
add coriander, green chilli, ginger and chopped dry coconut to the batter. mix it very well.
add 2-3 tsp of rice flour. rice flour is added to make it crispy.
add pinch of hing to make it more digestible.
heat the oil in a frying pan in medium flame. wet your palms and take a lemon size batter.
make hole in the center and slide it into the hot oil.
the vada should float on top of oil.
make sure your oil is not too hot. otherwise the vadas would not cook evenly.
fry on both sides till it becomes golden brown in colour.
serve medu vada immediately with chutney collections or sambar collections.