Melt the butter, then leave to cool down to room temperature.
Roll out the pastry until is about 5mm thick, if necessary.
Brush the cooled, melted butter onto the pastry, and roll the pastry up as tightly as possible. Refrigerate for at least 10-15 minutes.
Slice the rolled up puff pastry into 1cm disks.
Roll out the disks until they are about 8-10cm in diameter: the pastry should be practically paper thin.
Place the pastry in tart tins or muffin tins. Depending on the type of moulds you have, you may need to butter or oil them before filling with pastry.
Refrigerate the dough until needed.
Separate the eggs if necessary. Whisk the yolks to break them up, and set aside.
Stir a few tablespoons of the measured milk into the corn starch to make a slurry.
Bring the water and sugar up to the boil in a large pan. Leave to simmer until the sugar dissolves. Add the milk and corn flour slurry to the syrup. Bring back to a boil while stirring constantly.
Temper the egg yolks by slowly pouring the hot milk over them and whisking vigorously.
Pour everything back into the pan over a medium heat. Keep whisking until the custard thickens.
Transfer the custard into a bowl, cover with cling film on contact, and leave to cool to room temperature.
Pre-heat the oven to 200'C.
Fill the prepared tart shells with the custard.
Bake until the pastry is golden and flaky, and the custard begins to show some charred spots, about 15 minutes.
Serve warm or cool.
«You can flavour the custard with vanilla pod, pistachio or lemon zest. The tarts should be browned on the top, try using an overhead grill to finish this as desired. Traditionally served with sticky black coffee!!»