My first adventures into making vanilla slices was pretty much like this blog post As a generalisation I find these to be more like the mass produced variety, custard very firm and often with a thick icing. Almost indestructable and easy to cut and serve.
As time went by I discovered the joys of French pastry cream (creme patissiere) and this is more akin to those gourmet or artisinal offerings. There are are many interpretations of the icing - plain, passionfruit or simply dusted with icing sugar, however, the essence of the vanilla slice stays the same, a thick layer of good custard sandwiched between two sheets of crispy puff pastry. The custard recipe that I use was adapted from a Michel Roux recipe. His recipe uses only egg yolks but I use whole eggs and substitute cream for some of the milk and vanilla extract instead of a vanilla pod.
2 sheets puff pastry
1 -2 tablespoons raspberry jam, optional
icing sugar to serve
185 g sugar (3/4 cup)
60 g flour (4 tablespoons)
250 ml cream
2 teaspoons or more vanilla extract
Remove plastic film from pastry sheets and place on a tray to thaw. Prick all over with a fork and bake in a hot oven (200 deg C) until golden brown.
Remove from the oven and using a clean tea towel gently press the sheets flat.
Line the slice tray with foil or baking paper making sure that it extends over the sides so that you can lift the vanilla slice out.
Trim pastry sheets to fit. Place one sheet in the tray with the top side facing up. Spread a thin layer of jam over the pastry. The second sheet will be placed upside down later.
To Make the Custard
Combine milk, cream and two thirds of the sugar in a saucepan and bring to the boil.
Meanwhile whisk the remaining sugar with the eggs until slightly thickened and light ribbon consistency. Whisk in the flour making sure there are no lumps.
Pour the hot milk over the egg mixture, mix well and return the mixture to the saucepan. Bring the mixture to the boil, stirring continuously with the whisk. Let it bubble for a minute.
Pour custard over the pastry sheet in the slice tray and then top with the the remaining pastry sheet. Press firmly and refrigerate until cold.
Dust with icing sugar or a layer of thick icing.