1. combine custard powder, cornflour and sugar in large saucepan.
2. blend a little milk into the dry ingredients.
3. Add the remaining milk and chopped butter.
4. Bring to the boil, stirring all the time.
5. remove from the heat and add the vanilla and egg yolks.
TO MAKE SLICE
1. place sheets of puff pastry sheets onto a greased tray at 220 degrees for 10 mins. flatten the pastry.
2. place one piece on a slab tin to fit.
3. pour over custard and then put the other piece of pastry over the top.
4. ice with white icing.
5. refridgerate until set and cut into squares.
6. Serve and enjoy.
Sift icing sugar and add the melted butter and boiling water. mix well then pour over pastry.