Make pastry Process flour, sugar and butter until mixture resembles fine breadcrumbs. Add egg yolk. Process until dough just comes together, adding 1 tablespoon cold water if necessary. Turn onto a lightly floured surface. Knead until just smooth. Shape into a disc. Wrap in plastic wrap. Refrigerate for 30 minutes.
Preheat oven to 200°C/180°C fan-forced. Grease a 6cm-deep, 22cm (base) springform pan. Line base with baking paper. Roll pastry out between 2 sheets of baking paper until 5mm thick. Cut a 29cm round from pastry. Line pan with pastry. Refrigerate for 10 minutes.
Place pan on a baking tray. Line pastry case with baking paper. Fill with uncooked rice or ceramic pie weights. Bake for 10 to 12 minutes or until edge is light golden. Remove baking paper and rice or weights. Bake for 5 to 7 minutes or until base is light golden.
Reduce oven to 180°C/160°C fan-forced. Place plums in a bowl. Using a fork, lightly crush. Spread over base of pastry case.
Place vanilla bean and milk in a saucepan over medium heat. Cook for 3 minutes or until milk is hot (don't boil).
Whisk together eggs and sugar in a heatproof bowl. Remove and discard vanilla bean from milk mixture. Slowly add milk mixture to egg mixture, whisking constantly. Pour mixture over plums. Bake for 40 minutes or until custard is just set. Cool. Serve.
