Spinach, chard and chickpea puff pie

Method

1. Heat the oil in a large frying pan over a medium heat. Add the sliced onions with a pinch of salt and cook for about 15 minutes, stirring regularly. Finely slice the chard stalks (saving the leaves), add to the pan, then cook for another 15 minutes until very soft and light golden.
2. Meanwhile, put the chard leaves and spinach in a large colander over the sink and pour over a kettle of freshly boiled water to wilt them. Leave to drain for 10 minutes, then use a bowl or mug to press down and squeeze out more water. Once you’ve got rid of as much water as possible, transfer to a board and roughly chop the leaves.
3. Once the onions are very soft, add the garlic and chilli flakes. Cook for 2 minutes, then stir in the chard and spinach. Cook, stirring regularly, for 10 minutes. Roughly chop the pickled onions and add these to the pan. Add the chickpeas and cumin, then cook for 5 minutes more. Scrape into a bowl to cool, then chill for 30 minutes.
4. Heat the oven to 200°C fan/gas 7. Cut the block of pastry into 2 pieces, one slightly larger than the other. Lightly flour your work surface, then roll out both pieces, the smaller one to about 20cm x 26cm and the other about 5cm or so larger. Lift the larger pastry sheet into a baking tin so it reaches up the sides. Pile the chilled chickpea filling into the pastry case and spread evenly.
5. Brush the edge of the pastry with the milk alternative or beaten egg, then lay the second sheet of pastry on top as a lid. Use a fork or your fingers to crimp and seal the edge of the pastry all the way around. Brush the whole tart with the milk alternative or beaten egg. Imagine the pie divided up into 6 even squares, then use a small sharp knife to score a diagonal line on the lid of each piece.
6. Bake for 30-35 minutes or until rich golden brown. Leave to cool for 5 minutes before slicing and serving.