French Custard Tart

Instructions

1. Prepare the pastry
   On a lightly floured surface, roll out the pastry to fit a 9-inch (23cm) tart pan with removable bottom. Press the pastry into the pan, trimming any excess. Prick the bottom with a fork and refrigerate for 30 minutes.
2. Start the custard
   In a large saucepan, bring 800ml of the milk and the vanilla beans (if using) to a simmer over medium heat. In a large bowl, whisk together the eggs, sugar, cornstarch, and salt until smooth. Gradually whisk in the remaining cold milk to create a smooth mixture.
3. Cook the custard
   Once the milk in the saucepan is simmering, remove the vanilla beans (if using) and scrape the seeds into the milk. Slowly pour half of the hot milk into the egg mixture, whisking constantly. Pour this mixture back into the saucepan with the remaining hot milk. Cook over medium heat, whisking continuously, until the mixture thickens to a pudding-like consistency, about 3-4 minutes.
4. Finish the custard
   Remove from heat and stir in the butter pieces and vanilla extract (if using instead of beans). Whisk until butter is completely melted and incorporated. The custard should be very thick. Cover with plastic wrap directly on the surface to prevent a skin from forming and let cool for 10 minutes.
5. Assemble and bake
   Preheat oven to 375°F (190°C). Remove the tart shell from the refrigerator and brush the edges with egg yolk. Pour the slightly cooled custard into the shell, smoothing the top with a spatula. Bake for 45-50 minutes until the top is deeply caramelized and the custard is set but still has a slight wobble in the center.
6. Cool and serve
   Allow the tart to cool completely at room temperature, then refrigerate for at least 4 hours or overnight. The flan will firm up as it chills. For the authentic bakery look, the top should develop a brown, shiny crust. Serve cold, cut into slices.