Crispy Masala Dosa

Soak (start the day before)

1. Rinse and soak the rice. Rinse rice until the water runs mostly clear, then soak in plenty of water for 4 to 6 hours.
2. Rinse and soak the urad dal. Rinse urad dal and fenugreek seeds, then soak in plenty of water for 4 to 6 hours.
3. Soak the poha. About 10 minutes before blending, rinse poha and soak it in water for 10 minutes, then drain.

Blend and ferment

1. Blend the urad mixture. Drain the urad dal and fenugreek. Blend with cold water, adding a little at a time, until very smooth and fluffy. A helpful target is about 3/4 to 1 1/4 cups water total, depending on your blender and how well the dal soaked. The batter should look thick, airy, and glossy and mound softly in the bowl. Too much water here can make it less fluffy.
2. Blend the rice and poha. Drain the rice. Add the drained, soaked poha to the blender with the rice, then blend with water until smooth but with the tiniest bit of grit. Not sandy, just not baby-food smooth. If needed, do this in batches so your blender does not protest.
3. Combine and salt. In a large bowl, combine the urad batter and the rice-poha batter, then add salt. Mix with a clean hand for a minute or two (the warmth helps fermentation along). If you prefer, use a sturdy spoon or spatula and mix very well.
4. Ferment. Cover and let ferment in a warm spot for 8 to 14 hours, until slightly risen and bubbly. If your kitchen runs cool, aim for a warmer corner like an oven with the light on, or a microwave with a mug of hot water. An ideal range is about 75 to 90°F (24 to 32°C).
5. Adjust consistency. After fermenting, stir gently. Thin with water until the batter pours like heavy cream. It should still coat the ladle and flow in a steady ribbon. If it is too thick, it will not spread. If it is too thin, it will not crisp.

Make the potato masala filling

1. Temper the spices. Heat oil or ghee in a skillet over medium heat. Add mustard seeds and cumin seeds. When they start popping, add curry leaves.
2. Cook the aromatics. Add onion and cook until soft and lightly golden, 6 to 8 minutes. Add ginger and green chile (if using) and cook 30 seconds.
3. Season and mash. Stir in turmeric and salt. Add the mashed potatoes and toss to coat.
4. Loosen and finish. Add water and cook 2 to 3 minutes until the potatoes look creamy, not dry. Turn off heat, then stir in lemon juice and cilantro. Taste and adjust salt.

Cook the dosas

1. Heat the pan. Set a cast iron or nonstick skillet over medium-high heat. Sprinkle a few drops of water on the surface. They should sizzle and skitter, not just sit there and steam.
2. Lightly oil the surface. Rub the pan with a few drops of oil. Optional but excellent: wipe quickly with a halved onion dipped in oil for a super-thin coating.
3. Ladle and spread. Pour about 1/4 cup batter into the center. Immediately use the bottom of the ladle to spread it outward in quick circles into a thin round. Do not overthink it. Commit to the swirl.
4. Add fat for crisp. Drizzle 1 teaspoon oil or ghee around the edges and a few drops on top.
5. Cook until golden. Cook 2 to 4 minutes until the top looks set, the edges brown, and the dosa releases easily. For classic masala dosa, you typically do not flip. If you want extra color or you like a more evenly crisp finish, you can flip for 15 to 30 seconds.
6. Fill and fold. Spoon a line of potato masala down the center. Fold over like a wrap or fold into a triangle. Serve immediately with coconut chutney and sambar.
7. Repeat. Between dosas, reduce heat briefly if the pan gets too hot. Stir the batter occasionally, thinning with a splash of water if needed.