Heat the oil in a wok or wide pan over medium-high heat until it shimmers. Add the cumin and mustard seeds and heat until the mustard seeds begin to pop and crackle, about 30 seconds.

Add the garlic, ginger, and asafetida. Cook for a few seconds until the aromatics are fragrant, being careful not to let them burn.

Stir in the potatoes and salt, then lower the heat slightly. Cook for 6 to 8 minutes, stirring frequently, until the edges of the potatoes begin to turn golden brown.

Pour in the water and cover the pan with a tight-fitting lid. Reduce the heat to medium-low and simmer for about 8 minutes, until the potatoes are tender when pierced with a fork.

Remove the lid and increase the heat to medium. Add the methi, coriander, ground cumin, turmeric, and ground red chili, stirring constantly until the greens have wilted and the liquid has mostly evaporated, about 2 to 4 minutes.

Stir in the roasted cashews and squeeze on the lime juice. Adjust the seasoning with more salt if needed and serve warm.