Sweet potato and Swiss chard pie

To make pastry, add flour and salt to food processor and blend briefly.

Pour olive oil into a small jug, then add water and mix. With food processor running, pour oil and water into flour. Keep processing until dough forms a ball.

Lightly dust workbench with flour and knead dough for about a minute. Place dough in a large bowl, cover with a dry tea towel and leave for 1 hour to rest at room temperature.

Pre-heat oven to 200C.

For filling, remove leaves from chard stalks and finely chop stalks. Rinse leaves and chop, then place in a bowl with stalks.

Heat 1 tablespoon of oil in a heavy-based saucepan, add onion and cook for 5 minutes on a medium heat. Add chard and cook for another 5 minutes. Remove from saucepan and cool to room temperature. Add mozzarella, parsley and egg, and season. Boil sweet potato until tender, add to mixture.

Brush a flat baking tray with oil. Roll out two-thirds of the pastry into a large circle and lift onto tray.

Place filling onto pastry, leaving about 5 centimetres around the edge. Roll out remaining pastry for top of pie. Place over filling and squeeze together edges to seal the pie. Prick the top with a fork and brush with oil.

Bake for 25 minutes or until golden brown.