Preheat oven to 210 deg Celsius.
Line oven trays with baking paper and place one pastry sheet on each tray.
Prick with a fork, bake 10-15 mins Combine custard powder, sugar, and cream in a saucepan over medium heat.
Gradually add milk, stirring continuously until thick.
Add vanilla. · Cut cooked pastry to size of a brownie pan.
Layer pastry-custard-pastry in tray.
Make icing by combining butter, passion fruit and icing sugar over simmering water and mix until smooth.
Pour over top of slice.
Refrigerate.