These round loaves are stuffed with chickpeas, coconut milk, and spices. Serve warm from the oven with curry.
Place the flour into a large mixing bowl, or the bowl of a stand mixer, and mix in the yeast with your hand. When combined, mix in the curry powder and salt, then make a well in the centre. Pour in the oil and work in the flour, using your hand or the dough hook of the mixer (on the slowest speed). Gradually add lukewarm water until the dough is soft but not sticky.
Turn out the dough onto a lightly oiled worktop and knead for 10 minutes (or leave in the mixer and knead using the dough hook for 7 minutes on a slow speed), until the dough is smooth and elastic. Return the dough to the bowl (if necessary), then cover with cling film and leave to prove for about 1 hour, until doubled in size.
Meanwhile, make the filling. Heat the oil in a deep frying pan, add the mustard seeds and when they start to pop turn down the heat and stir in the onion. Cook gently for about 10 minutes, until the onion is soft and translucent. Stir in the garlic, turmeric, garam masala, cumin and curry powder and cook for 3–4 minutes.
Stir in the remaining ingredients, except the salt, then cook over a low heat for 10 minutes, until thick and fairly dry. Season with salt to taste. Transfer to a heatproof bowl and leave to cool.
Uncover the risen dough and punch it down. Turn out onto a lightly floured worktop, sprinkle with the nigella seeds and knead to distribute. Divide the dough into 4 equal portions.
Take 1 portion of dough and flatten it to a 17cm disc. Spoon 75g of the cooled filling into the centre. Gather up the edges and pinch to seal in the filling. Turn over the parcel and shape into a round bun, then flatten lightly. Transfer to the baking sheet. Repeat with the remaining dough portions. Cover and set aside the remaining filling. Loosely cover the buns with cling film and prove for about 1 hour, or until doubled in size.
Heat the oven to 220°C/200°C fan/425°F/Gas 7. Uncover the buns and bake for about 20 minutes, until golden brown, rotating the sheet after 15 minutes for an even bake. Transfer to a wire rack and cool slightly before serving. Reheat the remaining filling to serve alongside.