Soak urad dal for 4-5 hrs.
Heat oil in a flat vessel.
Add mustard seeds, when splutters add urad dal, curry leaves, and green chilies. When nicely fried, turn off the flame.
Add 1 cup of curd.
Also, add turmeric and salt and mix well.
Mix all the ingredients thoroughly and keep aside.
Meanwhile, heat oil in a deep frying pan or kadai.
Grind the dal in a blender by adding very little water to make a smooth and thick mixture. Add 1 tsp salt and mix well.
To make vada, dip your hand in the water, take a small lemon size urad dal mixture. Slightly make round and spread a little bit with thumb and make a hole at the center. You can also use a thick plastic cover or banana leaf.
When the oil is heat enough, slowly slip the vada into the oil.
On a medium flame, fry the vada till golden color on both sides.
Repeat step 4 to make all the vada's.
Put the fried vada in the prepared curd mixture.
Fully cover the vada with the curd mixture and allow the vada to absorb the curd completely.
Perugu garelu is ready. Serve immediately or can refrigerate and serve cold.