Indian masala dosas with spiced coconut potatoes

Method

1. Cook the potatoes in boiling water for 3-4 minutes until just firm when pierced with a sharp knife. Drain and steam dry in the pan.
2. Heat a large frying pan with a generous glug of groundnut oil. Add the mustard, cumin and fennel seeds, then cook over a medium heat, swirling the pan every so often, until the spices smell fragrant and the mustard seeds begin to pop.
3. Add the onion and fry for 5 minutes. Add the garlic, ginger, turmeric,cayenne and coriander, then fry until the spices smell rich and fragrant.
4. Add the potatoes to the pan with the curry leaves, green chilli, drained coconut and a splash of water to bring everything together. Cook for 5 minutes, stirring often and adding a little more water or oil if the mixture looks a bit dry. The potatoes should be almost completely broken down when ready. Squeeze over the lime juice, then cover the pan with a tight-fitting lid or foil and leave somewhere warm (or see Make Ahead).
5. To make the dosa batter, put the flours in a bowl with the bicarb and a good pinch of salt. Slowly whisk in around 300ml cold water with a balloon whisk to make a very loose and liquid batter.
6. Heat a 30cm frying pan over a medium heat, drizzle in a splash of oil and wipe it all around the pan with a piece of kitchen paper. When the pan is quite hot, add around 50ml batter, immediately swirling it so it covers the base of the pan very thinly (don’t worry if you don’t get an exact circle – you should have seen what some of our first attempts looked like!). Cook over a medium-low heat for around 8 minutes or until the top is dried out and the bottom is a pale golden colour (see tip). The edges should be crisp and wafer thin, and there should be tiny air bubbles all over the pancake.
7. Put a few spoonfuls of the potato mixture down the centre of the pancake, then roll up and slide onto a serving board or plate. Keep warm while you use up the remaining batter and potatoes, then serve with minted natural yogurt, if you like.