Preheat the oven to 200°C.
Cut the pastry into 18 equal sized rectangles and place on a lined baking sheet. Cover with a second sheet of baking paper and place a baking sheet on top. Transfer to the oven and bake for 15 to 20 minutes. Remove the top baking sheet and parchment, dust the pastry with icing sugar and then caramelise under the grill for 3 to 4 minutes. Set aside.
Split the vanilla pod in half and scrape out the seeds. Place the milk, vanilla pod and seeds in a pan and bring the milk to the boil.
Place the eggs and the sugar and whisk together. Mix in the flour and then add the hot vanilla infused milk. Stir together and then return to the pan and bring back to the boil. Cook for 3 minutes, stirring constantly. Pour the crème pâtissière into a flat dish and cover with cling film, pressing the cling film on to the surface of the mixture to prevent a skin forming. Chill in the fridge for 1 hour.
Once chilled, whisk the crème pâtissière until smooth. Whisk the double cream until thick and then fold into the crème pâtissière. Transfer to a piping bag and set aside.
Place the sugar in a frying pan and melt, without stirring, to form a caramel. Mix in the butter and the cream and then allow to cool.
Pipe the crème pâtissière on to 12 of the pastry rectangles and then layer them on top of each other so that you have six double layers of pastry and cream. Top each one with a final piece of pastry and serve with the salted butter caramel sauce.
«Vary the flavour of your crème pâtissière by replacing the vanilla with 50g of chestnut cream or pistachio paste.»