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. Flatten into a disk, wrap in plastic, and chill 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. 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.
04 - Heat milk and vanilla bean (seeds and pod) in medium saucepan over medium heat until just simmering. Remove pod.
05 - Whisk egg yolks, sugar, cornstarch, and salt in a bowl until pale and smooth.
06 - Slowly pour hot milk into egg mixture, 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.
07 - Transfer pastry cream to a bowl, cover with plastic wrap directly on surface, and chill until cold, at least 1 hour.
08 - 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.