Place the puff pastry sheets on baking trays lined with parchment paper. Prick the pastry with a fork all over to prevent puffing.
Cover with another sheet of parchment paper and place a second baking tray on top to weigh it down. This ensures even baking.
Bake for 12ā15 minutes, or until golden and crisp. Let cool, then trim the pastry to equal sizes.
2ļøā£ Make the Vanilla Custard:
In a saucepan, whisk together the egg yolks, sugar, cornstarch, and a splash of milk until smooth.
In another pot, heat the remaining milk until it just begins to simmer. Slowly pour the hot milk into the egg mixture, whisking constantly to temper the eggs.
Return the mixture to the saucepan and cook over medium heat, stirring constantly, until it thickens (about 4ā5 minutes). The custard should coat the back of a spoon.
Remove from heat, then stir in the butter, vanilla extract, and a pinch of salt (if using). Let cool slightly, then refrigerate until just warm or fully chilled.