Portuguese Custard Tarts

1 sheet puff pastry
3 egg yolks
1/2 cup castr sugar
2tbls cornflour
3/4 cup cream
1/2 cup milk
strip of lemon zest
2tsp vanilla extract

Preheat oven to 200c  Grease a muffin tray.
Cut pastry into 6cm rounds and press into muffin cups.  Refridgerate
Place yolks sugar and flour in a bowl and whisk to combine
Heat cream and milk in a pan until it comes to the boil and the surface is full of tiny bubbles. 
Pour the egg mixture in and stir in the lemon zest and vanilla.  Return the mixture to the pan and stir over medium heat until it almost comes to the boil...make sure it does not boil.  then take the pan off the heat. Remove and discard the zest
Fill the pastry cases with custard and bake for about 20 mins or until the topos are borned and pastry is crisp.  Cook on cake rack