Potato, brie and caramelised onion tart

Method

1. Preheat the oven to 200°C and place a baking tray in the oven. You need a 23 cm round flan (tart) pan with fluted sides and removable base.
2. To make the pastry, combine the flour, butter and sea salt in a food processor and pulse until the texture of fine breadcrumbs. Add the water and pulse until the dough starts to clump together. On a lightly floured work surface, knead the pastry until smooth, about 1 minute. Form the pastry into a disc with your hands and cover in plastic wrap. Refrigerate for 20 minutes.
3. To make the filling, heat the olive oil and butter in a medium frying pan over medium heat. Add the sliced onions and fry, stirring occasionally, until you start to see touches of gold on the onions, about 4 minutes. Reduce the heat to medium–low and cook, stirring occasionally, until the onions are very soft and golden brown, about 20 minutes.
4. Put the potatoes and salt in a small saucepan and cover with cold water. Bring to the boil over medium–high heat and boil until tender, about 6–8 minutes, testing with the point of a sharp knife. Drain the potatoes and return them to the saucepan over low heat for 1 minute to ensure any excess water has evaporated.
5. Meanwhile, on a lightly floured work surface, roll out the pastry into a circle about 3 mm thick. Line the flan pan with the pastry, taking care when pressing into the fluted sides. Trim the overhang, leaving a 5 mm lip around the edge of the pan to allow for shrinkage. Place the pan on the baking tray. Prick the pastry with a fork in a few places and chill in the refrigerator for 15 minutes.
6. To blind bake the pastry, cover it with a sheet of baking paper and fill with pie weights or uncooked rice. Bake for 15 minutes. Remove the weights and the baking paper and return the pastry to the oven until the pastry looks dry and lightly golden, about 10 minutes. Sprinkle the pastry with the parmesan cheese and set aside for 5 minutes.
7. Reduce the oven heat to 170°C.
8. In a medium mixing bowl, whisk the cream, eggs, sea salt and pepper together until smooth.
9. To assemble the tart for baking, spread the onions over the parmesan in the pastry case. Layer the potato slices on top of the onions, followed by the brie. Sprinkle with the thyme leaves. Gently pour the egg mixture over the top.
10. Bake the tart until it is puffed and golden, about 40–45 minutes. Sprinkle with thyme and allow to cool for a few minutes before removing from the pan and slicing.