1. Preheat an oven to 200 degrees celsius and grease a 12 hole muffin tin with butter or margarine.
2. Cut the puff pastry sheet in half (so there are 2 rectangle shapes), then place one rectangle directly on the of the other and roll it up from the short end so it becomes a tube about 10cm long.
3. Cut 12 even discs of pastry from the tube, then on a lightly floured board (cornflour is best), roll each disc out into a thin circle about 10cm wide. Mould each into the muffin tin, then set to the side.
Custard (this is so yummy as an everyday custard too!)
4. In a cold saucepan, whisk the egg yolks, sugar and cornflour together.
5. Gradually whisk in the milk, then place over a medium hot plate, stirring constantly till custard starts to boil and thicken (the custard will go from runny to thick quite suddenly, so don't get distracted!).
6. Stir through the vanilla extract (try to avoid essence), before pouring into a heatproof bowl covered with cling wrap (to prevent the custard forming a skin). Allow to cool.
7. Spoon equal amounts of custard into each pastry case (about 1-2 tablespoons) before baking for 20-25 minutes till golden.
TIP. If you want the slightly blackened tops, the oven cooking alone may not achieve this (depending on your oven). Try taking them out after 20 minutes of baking and place the tray under a grill - the direct heat should react with the sugar pretty quickly, giving a lovely rich colour.