Prepare the potato filling: Boil potatoes with salt, sugar, and vinegar until tender.

Drain potatoes and sprinkle with vinegar.

Sauté onions in ghee until browned.

Temper mustard seeds, cumin seeds, and chana dal in the ghee.

Add turmeric, red chili, asafetida, green chili, and cashews; cook until fragrant.

Add cooked potatoes, sugar, cilantro, browned onions, and water.

Simmer until the filling ingredients combine and a light sauce forms; season with salt.

Prepare the dosa: Preheat a cast iron griddle over medium heat.

Pour batter onto the center of the griddle and spread thinly in a circular motion.

Cook until the surface is set, about 1 minute.

Brush with melted ghee and continue cooking until the bottom is golden brown and the edges are crisp, about 4 minutes longer.

Top each dosa with 1/2 cup of warm potato masala.

Roll each dosa and serve immediately with coconut chutney.