Divide the pastry into six equal pieces, shape each one into a ball. Roll each ball out on a lightly floured surface and press into a 8-9cm/3.25-3.5in tart tin, pressing it right into the corners and leaving the excess pastry overhanging. Repeat for the rest of the pastry.
Prick the base of each pastry case all over with a fork, place them on a baking sheet and pop it in the freezer (or fridge if it wont fit), for fifteen minutes (or thirty in the fridge) while you preheat the oven to 180°C/350°F/gas mark 4.
To make the pastry cream, whisk together the egg, egg yolks, cornflour, sugar and vanilla extract in a heatproof bowl until thick and pale.