Warm oil in a saute pan or kadai or a wok. Reduce the heat, add the cumin seeds and mustard seeds, let the seeds pop. Add asafoetida, onions, curry leaves, green chili, ginger, turmeric, and sauté for 2-3 minutes until onions are translucent.
Add boiled potato, salt to taste. Mix well. Add about ¼ cup of water, over and cook the mixture for 3-4 minutes. If you like you could use the back of a spatula and mash some of the potatoes for texture.
Garnish with some fresh cilantro and lemon juice. Taste and Serve.