1. Preheat your oven to 180°C (350°F). In a saucepan, heat the milk with the split and scraped vanilla bean until it boils. Remove the vanilla bean.
2. In a bowl, whisk the egg yolks with the sugar until the mixture whitens.
3. Add the sifted cornstarch to the egg yolk mixture and mix well until you get a smooth paste. Slowly pour the hot milk over the mixture while stirring constantly.
4. Pour the mixture back into the saucepan and cook over low heat, stirring constantly until the cream thickens.
5. Roll out the shortcrust pastry in a buttered tart pan. Pour the custard over the pastry and smooth the surface.
6. Place the pan in the middle of the oven and bake for about 40 minutes, until the custard is golden and firm.