Into a bowl add semolina, chopped onions, chopped green chilies, chopped ginger, cumin seeds, chopped curry leaves, asafoetida, salt to taste. Mix well.
Add 1 tablespoon yogurt at a time and mix well. Keep adding yogurt little at a time and mix until you get a batter that has the consistency of medhu vada batter(not too runny or too thick)
Cover and rest the batter for 15 minutes while you heat oil in a deep bottom pan for deep frying.
Before frying, mix batter for 1 or 2 minutes well.
Wet your right hand well by dipping inside water and take a small ball of batter. Shape into round and then flatten into a disc shape. Now use your thumb to make hole in the middle and drop it in oil (you can follow banana leaf method where the vadas are shaped on banana leaf and then slide the shaped vadas into hot oil)
Be very careful while doing this and stand as far as possible from hot oil. DEFINITELY no kids around you while you are deep frying the vadas.
Fry on medium-low flame, turn the vadas and fry till both the sides turn crisp and golden brown.
Remove from oil and let it sit on kitchen towel for excess oil to be absorbed. Repeat the process for rest of the batter.
Crunchy hot and delicious vadas are ready to be served. The vadas are best when paired with Chutney and Sambar. DELICIOUS!