Custard slices

1 sheet of thawed puff pastry, cut in half
1/2  cup sugar
1/2 cup custard powder
2 cups milk
1 teaspoons vanilla

Directions:

1 Place piece greaseproof paper onto a flat biscuit tray. Put puff pastry on tray and pierce all over with a fork, but don't go all the way through pastry.
2 Put in oven  (200°C) until puffed up and golden.
3 Let cool for a few minutes and gently pat pastry down so it's flat. Take it off baking tray and remove paper.
4 Put pastry into a square dish (6-7 inch) that has been greased and lined with greaseproof paper.
If pastry too big trim the sides a little. It should be a snug fit.
5  Set pastry to one side until custard is done.
6 For the custard, put the sugar, milk and custard powder into a large saucepan and mix together with a wire whisk.
7 Add the vanilla and mix to combine well.
8 Put saucepan on stovetop and heat on medium high until mixture begins to thicken, then immediately lower the heat until mixture is very thick and hard to stir.
9 Pour into prepared dish.
10 Smooth top so it's even and put 2nd pastry sheet on top.  Leave to cool.
11 Melt about 1 tablespoon of butter with 1 teaspoon boiling water. Then add icing sugar,and a bit of water or lemon juice until it's the right consistency and amount-not  too runny.
12 Pour the icing on top and put in fridge for a few hours or overnight.
13 Cut into squares and enjoy!

I have been told to use only Bird's custard powder, however I've never used any other kind so I can't say if it works with other brands.  The slower the custard is cooked the better - keep stirring well.