In a pan heat oil, add mustard seed, split black gram once the mustard seed stop splattering add the onion, green chili and cook until onion turns golden brown. Now add this to the batter and mix well.
Heat the kuzhi paniyaram pan with oil in the kuzhi. Pour the batter into the kuzhi.
When cooked (turn golden brown) flip over and cook the other side. When cooked on the other side remove them and serve.