Wash and soak the dal overnight. Drain and then grind it to a smooth paste without using water. Transfer the paste into a bowl. Add asafoetida, ginger and green chilli pastes and mix well.
Grease a tray or a thali. Put the mixture in a piping bag and press out small dumplings onto the greased thali. You can do this using your fingers too. Sun dry the mangodis for a day or two or till completely dry.
When cooled store them in an air tight container and use as required.