Take one pan and add one tablespoon oil. Heat on medium heat. Now add mustard seeds. When the mustard seeds crackle, add hing and curry leaves. Now add chopped onion and saute for 1 minute. Now add tomato chutney and mix well. If you don't have tomato chutney, you can use chopped tomatoes with dry spices. Add salt and mix well. Now add fried Idli pieces and mix everything well.