Wash urad dal under running cold water till water runs clear.Soak it in enough water for at least 4-5 hours.

Making vada:
Drain the soaking water completely. Add that to the blender or grinder.
Make smooth paste out of it. Use ½ cup of water while grinding the dal. Remove it to a bowl.

Add chopped green chilies, salt and baking soda. Mix well.
Now using a spatula or by hand, beat the batter for good 5 minutes.
Beat it till batter gets light and fluffy.
Now check the right batter consistency. Take water in a small bowl or katori. drop a teaspoon of batter into the water. It should be floating on top. If it sinks to the bottom means batter has thin consistency. Adjust it by adding couple of tablespoons of semolinat

Now heat the oil in a pan on medium heat for frying the vadas.
Once hot drop the vadas using two spoons or by hand.
Fry the vada on medium heat. Keep moving to get even cooking and browning.
Fry till they are crispy and golden brown in colour. You will have to fry them in batches.
Remove it to a paper towel lined plate.

Take water in a large vessel or bowl. Add the warm vada into the water.
Keep frying and adding them into the water. Let it soak for 30-40 minutes.
After that we need to squeeze the excess water. Very lightly press it between your plam.

Making dahi mixture:

Take yogurt in a bowl.
Add red chilli powder, roasted cumin powder and salt.

Whisk it till it gets smooth. Keep refrigerated till needed.

Prepare imli chutneys--Soak the tamarind in 3 cups of hot water for 20 minutes.Mash it using hands and strain it through a soup strainer.Discard the tamarind pulp and keep the water.In karahi add hing, kashmiri mirch, panchphoran, then add tamarind water in a pan.Add sugar and all the remaining ingredients.Cook the mixture on medium heat for 10-12 minutes.Keep stirring at regular intervals.Remove the pan from heat and keep on.