Peel and chop the boiled potatoes. Set aside.
Heat oil in apan.
Add mustard seeds and let them splutter.
Add cumin seeds, asafoetida,chopped ginger, and curry leaves. Sauté for a few seconds.
Add chopped green chillies and onions. Sauté till the onions turn soft and translucent.
Add turmeric powder and salt. Mix well.
Add the chopped boiled potatoes and hot water.
Mix everything together and mash the potatoes slightly for a semi-thick consistency.
Add a pinch of sugar if using.
Simmer for a few minutes to let the flavours blend. Turn off the heat.
Garnish with chopped coriander leaves.
Serve hot with puri, chapati or Goan pav (bread)