Leek and Gruyère Tart

Combine the flour and ½ teaspoon salt in a large bowl. Add 150g cold cubed butter and rub between your fingertips until the mixture resembles coarse breadcrumbs with some pea-sized pieces remaining. Drizzle in the ice water one tablespoon at a time, mixing with a fork just until the dough comes together.

Shape the dough into a flat disc, wrap and refrigerate for at least 1 hour.

Wash the sliced leeks thoroughly in a large bowl of cold water, agitating to release grit, then drain and spin or pat dry.

Melt the remaining 50g butter in a wide, heavy-bottomed pan over medium-low heat. Add the leeks, remaining ½ teaspoon salt and thyme. Stir to coat, then cover and cook for 20 minutes, stirring every 5 minutes, until completely collapsed and tender.

Uncover, add the garlic and white wine, and increase the heat to medium. Cook for a further 8–10 minutes, stirring frequently, until all liquid has evaporated and the leeks are golden and jammy at the edges.

Remove from heat and allow the leeks to cool to room temperature.

Preheat the oven to 190°C, or 170°C for a fan oven, or 375°F with a heavy baking sheet on the middle rack.

On a lightly floured surface, roll the chilled pastry into a circle approximately 30cm in diameter and 3mm thick. Drape over a 23cm loose-bottomed tart tin, press into the sides, and trim the overhang to 1cm above the rim. Prick the base all over with a fork, line with baking paper, and fill with baking weights or dried beans.

Slide the tart tin onto the hot baking sheet and blind bake for 18 minutes, until the edges are set and pale golden.

Remove the baking paper and weights and return the tin to the oven for a further 6 minutes, until the base is dry and just beginning to colour. Remove and reduce oven temperature to 170°C, or 150°C for a fan oven, or 340°F.

Whisk together the eggs, double cream, milk, nutmeg, white pepper and half the Gruyère in a jug until smooth.

Scatter the cooled leeks evenly over the pastry base. Pour the custard mixture over the leeks, then top with the remaining Gruyère.

Bake for 30–35 minutes, until the custard is just set with a very slight wobble at the very centre and the top is deep golden. A digital thermometer inserted into the centre should read 80°C.

Allow the tart to rest in the tin for 15 minutes before unmoulding and slicing. Serve warm or at room temperature.