In a mixing bowl, combine the flour, salt and whisk well. Add water to make a thick batter. Add water very slowly, so that you won't end up with watery batter, you want it to be thick. Cover and set aside for at least 1 hour and for up to 3 hours.
Stir in onion, curry leaves, green chilies, and salt. Mix well. Just before making the vadas, add the baking soda and mix well again.
Heat oil for deep frying. Take a small lemon size ball of the batter and place it on a damp plastic ziploc bag or your palm. Flatten it slightly and poke a hole right in the middle (as in a donut or bagel). Gently slide the vada into the hot oil and fry on medium flame until golden. Flip carefully and fry on the second size until golden. Fry 3~4 vada at a time depending on the size of your pan. Repeat with rest of the batter.Remove using a slotted spoon onto a paper towel lined plate. Repeat with the remaining batter. Serve hot with chutney.
e not to add too much water to urad flour. If the batter is too watery, it will be difficult to shape the vada. But if you happen to add a little too much water to the batter, then add a few tablespoons of rice flour or all purpose flour. Mix well and fry as usual.
Soaking urad flour helps with making a soft vadai. So soak it for as long as you can.
If you think shaping medu vada or vadai with hole is hard, then simply make pakoda. That is drop the batter into the oil using a spoon.
Omit adding onion if you are making these for a festival. But you can substitute it with finely shredded cabbage instead.
Add baking soda just before making the vada and make sure to stir it in well. This ensures that the instant vada are airy and light inside.
Make sure that the oil is hot enough before adding the batter. Test by adding a drop of batter, if it starts to sizzle then it's ready for frying. If not, heat oil for a minute more.
To make sure that the inside of the vada is cooked properly, fry them until the bubbles and sizzles around them get smaller.
Remove the fried vada onto a paper towel lined plate to absorb any excess oil.
Vada are best when eaten hot. If you happen to have any leftovers, then store them at room temperature for 1 day.