01 - Pulse flour, powdered sugar, and salt in a food processor to combine. Add cold butter and pulse until mixture resembles coarse crumbs. Add egg yolk and pulse again. Add ice water 1 tablespoon at a time just until dough comes together.
02 - Flatten dough into a disk, wrap in plastic, and refrigerate for at least 1 hour.
03 - Preheat oven to 350°F.
04 - On a lightly floured surface, roll out dough to fit a 9-inch tart pan. Press into pan and trim excess. Prick base with fork.
05 - Line crust with parchment and fill with pie weights or dried beans. Bake for 15 minutes. Remove weights and parchment, then bake for another 8-10 minutes until golden. Let cool completely.
06 - In a medium saucepan, heat milk and vanilla bean (seeds and pod) over medium heat until just simmering. Remove pod.
07 - Whisk egg yolks, sugar, cornstarch, and salt in a bowl until pale and smooth.
08 - Slowly pour hot milk into egg mixture while whisking constantly. Return mixture to saucepan and cook over medium heat, whisking constantly, until thick and bubbling for 2-3 minutes.
09 - Remove from heat and stir in butter until smooth. Transfer to bowl and cover with plastic wrap directly on surface. Refrigerate until cold, at least 1 hour.
10 - Spread chilled pastry cream evenly into cooled tart shell. Top with fresh berries if desired. Dust with powdered sugar before serving.