01 - Pulse flour, powdered sugar, and salt in a food processor until combined. 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. Flatten into a disk, wrap in plastic, and refrigerate for at least 1 hour.
02 - Preheat oven to 350°F.
03 - 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.
04 - 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.
05 - Heat milk and vanilla bean (seeds and pod) in medium saucepan over medium heat until just simmering. Remove pod.
06 - Whisk egg yolks, sugar, cornstarch, and salt in a bowl until pale and smooth.
07 - 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, about 2-3 minutes. Remove from heat and stir in butter until smooth.
08 - Transfer pastry cream to a bowl, cover with plastic wrap directly on surface, and refrigerate until cold, at least 1 hour.
09 - Spread chilled pastry cream evenly into cooled tart shell. Top with fresh berries or fruit if desired. Dust with powdered sugar before serving if desired.