Masala dosa

Step 1: Rinse 10 ½ oz parboiled rice (idli rice) in several changes of water until it runs clear, and soak it in a bowl with 1 oz thick poha (flattened rice). In a second bowl, soak 3 ½ oz whole skinless urad dal, 1 tbsp chana dal and 1 tsp fenugreek seeds. Leave both for 5 hours.

Step 2: Drain the urad dal and grind it with a little of 1 ½ cups cold water for 8–10 minutes, adding water a spoonful at a time, until it is very smooth, fluffy and pale and has roughly doubled in volume. Air whipped in here is what lifts the batter, so don't drown it in water.

Step 3: Drain and grind the rice and poha with more of the water to a fine paste with a very slight grit, like fine semolina, about 8 minutes. Combine both batters in a large bowl (it should come no more than halfway up) with 1 ½ tsp salt and mix with your hand for a minute; the warmth and natural yeasts on your hand help the ferment.

Step 4: Cover loosely and leave in a warm spot (around 28–90°F; an oven with just the light on works in a cool kitchen) for 8–12 hours. It's ready when it has risen by about half, looks bubbly and spongy and smells pleasantly sour. Stir gently; it should flow like thick pancake batter. Thin with a little water if needed.

Step 5: For the potato masala, heat 2 tbsp vegetable oil in a pan over a medium heat. Add 1 tsp black mustard seeds and when the seeds pop, add 1 tsp urad dal and 1 tsp chana dal and fry until golden, about 30 seconds. Add 12 fresh curry leaves (they will spit) and ¼ tsp gluten-free asafoetida (hing).

Step 6: Add 2 onions, 3 green chillies and 1 tbsp fresh ginger and cook for 4–5 minutes until the onions are soft and translucent but not brown. South Indian masala keeps the onion sweet and pale.

Step 7: Add ½ tsp ground turmeric, 1 tsp salt and ½ cup water, then 1 ⅛ lb potatoes. Stir and cook for 3–4 minutes, crushing lightly, until it's soft and holds together but still has some chunks. Off the heat, stir in 1 tbsp lemon juice and 2 tbsp fresh coriander.

Step 8: Heat a large cast-iron griddle or non-stick pan over a medium-high heat for 3–4 minutes. Rub it with ½ onion dipped in a little of 4 tbsp vegetable or sesame oil, then sprinkle with a few drops of water; they should skitter and vanish. Turn the heat to medium.

Step 9: Pour a ladle (about 80 ml) of batter into the centre and immediately spread it in quick outward spirals with the back of the ladle into a thin 25 cm round. Work fast and lightly; pressing hard leaves bare patches.

Step 10: Drizzle ½ teaspoon of oil over and around the edge. Cook for 1½–2 minutes without moving it, until the underside is golden brown, the top looks dry and the edges lift away from the pan by themselves. Don't flip.

Step 11: Spoon 3 tablespoons of potato masala along the middle, fold or roll the dosa over it and slide onto a plate. Before the next dosa, sprinkle the griddle with water and wipe with the onion to bring the temperature down a touch; too-hot pans make the batter clump instead of spreading.

Step 12: Serve each dosa the moment it's made, with coconut chutney and sambar if you like. The leftover batter keeps in the fridge for 3 days and gets tangier.