Preheat your oven to 200°C/180°C/Gas Mark 6 and line 2 baking trays with baking parchment. 

Unroll your puff pastry and cut into 2 x 8” squares and place each square of pastry onto a lined baking tray. Top tip; try cutting the pastry with a pizza cutter to get a neat line. Cover each pastry square with some more parchment paper and then place a baking tray on top, this stops the pastry puffing up too much whilst baking.

Bake the pastry for 20-25 minutes until golden brown and place on a cooling rack to cool completely. 

Whilst the pastry is baking it’s time to make the custard. Pop the egg yolks, caster sugar and corn flour in a bowl and whisk together to make a smooth paste.

Pour the milk and Vanilla Paste into a saucepan and pop over a medium heat stirring until simmering. Pour half the hot milk mixture into the egg yolk mixture and whisk to combine. Pour back into the remaining milk mixture. Pop the pan back over a medium heat and continuously whisk until the mixture begins to bubble. As it bubbles it’ll thicken, continue to whisk for about 1 minute seconds and then remove from the heat, make sure your custard has thickened and boiled before removing from the heat as this will help it set. Pop in the butter and stir until it has melted into the custard. 

Pour into a bowl and cover with cling film, ensuring the cling film touches the surface of the custard as this will prevent a skin from forming on the custard. Leave to cool to room temperature.

Once your custard has cooled, it’s time to assemble your custard slices! Line an 8” square tin with foil, make sure the foil folds over the edges of the tin, this will create a handle so you can lift the slices out of the tray when ready to serve. 

Pop one square of pastry into the base of the tin, trim it down slightly it is too big. Briefly whisk your custard to loosen it and pour over the pastry and smooth out to cover the pastry and make sure there is an even layer of custard. 

Pop the final square of pastry on top, again trim off any excess if needed and press lightly so it touches the custard layer. 

Now it’s time to decorate your custard slices. Break the white chocolate into pieces and pop into a large bowl. Melt the chocolate in the microwave for 30 second bursts stirring the Chocolate between each burst until it has melted. Repeat for the Dark Chocolate and pop it in a piping bag once it has melted. 

Pour the White Chocolate over the top of the pastry and smooth to cover the pastry top in melted chocolate. 

Now for the feathering! Snip the end off the piping bag and pipe horizontal lines of chocolate spaced about 1-2cm apart over the top of the white chocolate. Grab a cocktail stick and pull through the dark chocolate lines vertically backwards and forwards to create the feathered chocolate effect.

Pop your custard slice in the fridge until ready to serve and the chocolate has set. Slice up using a hot knife whilst your bake is still in the tin and then remove from the tin using the foil handles to help. Store your custard slices in the fridge and they will keep for up to 3 days, if they stick around that long!