Wash the parboiled rice and urad dal separately until the water runs clear. Drain and set aside.

Soak the rice in 1 cup of water and the dal with fenugreek in 1/2 cup of water for 4–5 hours.

Drain the soaked rice and dal. Transfer to a grinder, add 1 tsp salt, and grind to a smooth, slightly gritty batter, adding water as needed to achieve a pourable consistency.

Transfer the batter to a wide bowl, cover with a lid or cloth, and let it ferment at room temperature for 8–12 hours until it rises and develops a mild tang.

Heat a non‑stick griddle or cast‑iron tava on medium‑high flame. Add 1 tsp oil and swirl to coat the surface.

Pour a ladleful of fermented batter onto the center of the hot pan. Immediately tilt the pan to spread the batter into a thin, even circle, about 8–10 cm in diameter.

Cook for 2–3 minutes on medium flame until the edges lift and the surface turns golden‑brown and crisp. Do not flip; the dosa should stay thin and paper‑like.

Remove the dosa, place on a plate, and repeat with remaining batter to make 4 dosas.

Boil the potatoes in lightly salted water until just tender (about 10 minutes). Drain, peel, and mash with a fork.

Heat 1 tbsp oil in a pan on medium flame. Add mustard seeds and cumin seeds; wait for them to crackle.

Add finely chopped onion and green chili; sauté until the onion turns translucent (3 minutes).

Stir in ginger‑garlic paste and cook for 1 minute until the raw aroma disappears.

Add turmeric, red chili powder, coriander powder, and garam masala; cook for 30 seconds, stirring constantly.

Introduce the mashed potatoes, mix well, and season with salt. Cook on low flame for 5 minutes, allowing the spices to coat the potatoes and the mixture to thicken slightly.

Finish with chopped coriander leaves and a splash of lemon juice for brightness.

Spread a thin layer of red chutney on one side of each dosa. Spoon a generous portion of aloo masala onto the chutney‑side.

Fold the dosa over the filling to form a semi‑circle. Gently press the edges to seal.

Serve hot, accompanied by fresh coconut chutney or a side of plain yogurt if desired.