Step 1: Prepare the Dosa Batter
1. Rinse rice, urad dal, chana dal, and fenugreek seeds separately, then soak them in water for 4–6 hours.
2. Soak poha for 30 minutes before grinding.
3. Drain and grind everything into a smooth, slightly thick batter using minimal water.
4. Transfer to a large bowl, cover, and allow it to ferment for 8–12 hours (overnight) in a warm place. The batter should double in volume and become airy.
5. After fermentation, add salt and mix gently.

Step 2: Make the Potato Masala Filling
1. Heat oil in a pan. Add mustard seeds and let them splutter.
2. Add urad dal, chana dal, curry leaves, and green chilies. Sauté until dals turn golden.
3. Add onions and ginger, cook until onions turn soft and translucent.
4. Mix in turmeric powder and salt.
5. Add boiled, mashed potatoes and mix well. Sprinkle some water if needed to keep it moist.
6. Finish with chopped coriander. Set aside.

Step 3: Cook the Dosa.
1. Heat a non-stick or cast-iron tawa (griddle) on medium flame.
2. Lightly grease with oil or ghee.
3. Pour a ladle of batter in the center and spread outward in a circular motion to make a thin dosa.
4. Drizzle a few drops of oil/ghee around the edges.
5. Cook until golden and crisp. (No need to flip if it’s thin and cooked well).

Step 4: Assemble Masala Dosa
1. Place 2–3 spoonfuls of potato masala in the center of the dosa.
2. Fold the dosa into a roll or triangle.
3. Serve hot with coconut chutney and sambar.