A recipe from the Good Food collection.
2½ cups (310 g) plain flour
1 teaspoon baking powder
1/4 cup (60 ml) oil
2 eggs, lightly beaten
1 egg yolk, lightly beaten
35 g butter
2 onions, finely chopped
1 large starchy potato, unpeeled, quartered
1. Combine the flour, baking powder and ½ teaspoon salt in a large bowl. Make a well in the centre and add the oil, whole eggs, and ¼ cup (60 ml) water. Gradually mix in the wet ingredients with a wooden spoon. Knead for 10 minutes, sprinkling with extra flour if necessary. Coat the dough with oil, wrap with plastic wrap and leave for 1 hour.
2. To make the filling, heat 20 g of the butter in a frying pan over medium heat. Add the onion and cook for 10 minutes, or until soft and slightly brown. Bring a large saucepan of water to the boil. Add the potato and boil for 12 minutes, or until soft. When cool enough to handle, peel, then mash to a coarse paste with the remaining butter. Add the onion and season.
3. Preheat the oven to moderate 180°C (350°F/Gas 4). Knead the dough briefly, cut in half and set aside for 5 minutes. Working with one piece of dough at a time, roll out as thin as you can (about 2–3 mm). Cut into 12 cm rounds. Pull the dough if it springs back. Place 1 heaped tablespoon of the filling in the centre of each round, brush the edges with a little water and bring the edges into the middle, pinching to seal them. Place on a greased baking tray, brush with egg yolk and bake for 20–25 minutes, or until golden. Serve hot or warm.