Trim the edges of bread slices and cut into cubes.
Add yogurt and rice flour and mix until well combined or bread is mashed.
Add the chopped onion, green chillies, ginger, curry leaves, cumin seeds, salt and baking soda to the bread mixture and mix well to form a thick batter.
Add little more yogurt or rice flour to adjust the consistency
Heat oil in a pan for deep frying the vadas.
Wet your fingers and take a small portion of vada batter and flatten it on your palm or on a plastic sheet.
Make a small hole in the middle of the vada and slowly drop it in the hot oil.
Fry them until golden brown on both sides.
Drain on a paper towel and serve hot with chutney or tomato sauce.