Boil the Potatoes. Peel and smash them along with green chillies, leaving some pieces. Add salt. Also add about 1/2 cup of water in which the potatoes were boiled.
In a pan, heat about 1 tbsp oil. Once the oil is heated, add mustard. When the mustard crackles, add red chilly, Asafoetida and curry leaves. Add this to the smashed potatoes. Mix well. Serve warm or cold.
The same when made more liquidy can be used for rice. But it must be served warm for rice. If you want to eat it like a spicy salad (which Indians prefer), serve it cold.