Take 1 cup urad dal in a small deep pot. Wash it 2-3 times in water. And add two cups water then soak it 2-3 hours.
Drain access water in the dal. Transfer it to the mixer jar of a blender.
Grind until the batter is fluffy and have a smooth texture. Don’t add too much water while grinding add less than half cup water.
Transfer batter into a bowl. And beat it using your hand for 2 minutes in one direction.
Add 1 chopped onion, 1 tsp cumin seeds, 1/2 tsp crushed black peppercorns, chopped curry leaves, a pinch of Hing, chopped green chillies, coriander leaves chopped and salt to taste and Mix well.
Heat oil in a deep kadhai or pan over medium flame.
Wet your palm with water. Take a medium lemon sized portion of batter on your palm, press it gently and make thick round shaped vada.
Next, Make a hole in the centre using your finger.
When the oil is medium hot slowly slide vada in it.
Flip and deep fry both the sides until they turn lightly golden brown and crisp.
Repeat the same process for remaining batter. Spongy medu vada is ready to serve with chutney or hot sambhar.