Chard, feta & sesame pie with olive oil pastry

First make the pastry. Weigh the flour into a bowl, add 1 tsp fine salt and drizzle over the olive oil. Mix the oil into the flour using a fork. In a separate bowl, mix the beaten egg with 100ml cold water, set aside 1 tbsp of the mixture for glazing, and pour the rest into the flour. Stir with a cutlery knife until the mixture starts to form clumps, then tip onto your work surface and knead to a dough. It may feel a little crumbly but keep squeezing together until any flaky bits are worked into the dough and you have a smooth ball. Break the dough into two pieces, put back in the bowl and cover with a tea towel. Leave to rest while you prepare the filling.

Heat the oil in a large frying pan. Add the leeks and a pinch of salt, cook over a low-medium heat, stirring occasionally, for around 10 mins, until the leeks collapse and start to caramelise.

Meanwhile, strip the leaves from the chard stalks. Finely chop the stalks and put the leaves in a colander. Pour a kettle of boiled water over the leaves, leave to cool for a minute, then squeeze out as much of the liquid as you can and finely chop.

Stir the garlic and chard stalks into the leeks, cook for 2-3 mins until the stalks have softened, then stir in the chopped leaves. Add the herbs, lemon zest and juice, tahini, sumac and chilli. Cook for 1-2 mins until no liquid remains. Tip the mixture into a bowl and leave to cool.

Mix the feta into the chard and season. Will keep chilled for a day.

Heat the oven to 200C/180C fan/gas 6. Put one ball of pastry between two sheets of baking parchment. Gently roll out the pastry until you have a circle, roughly 28cm in diameter and about the thickness of a £1 coin. Remove the top sheet of parchment and lift the pastry onto a baking sheet.

Spoon the cooled chard into the centre of the pastry, leaving a border of about 2cm. Brush a little of the beaten egg and water mixture around the border.

Roll out the second ball of pastry in the same way as the first piece. Carefully lay it over the filling. Roll the pastry edges towards the centre of the pie and crimp the two layers of pastry together to seal. Brush the pie with the egg and water mixture and sprinkle generously with sesame seeds. Cut a few steam holes into the pastry with a sharp knife – a cross in the middle, then slits all around.

Bake for 50 mins-1 hr, until the pastry is deep, golden brown. Leave to cool for 15 mins before eating. Will keep chilled for two days.