2 x 25cm square sheets pre-rolled butter puff pastry
½ cup caster sugar
1 tablespoon butter
1 teaspoon vanilla bean paste
¼ teaspoon sea salt
6 large egg yolks, size 7
⅓ cup cornflour
150 grams chopped chocolate (I used Whittakers Marlborough Sea Salt and Caramel Brittle)
2 tablespoons cream
1 tablespoon water
½ teaspoon vanilla bean paste
1½ cups icing sugar, sifted
reserved pastry trimmings
extra chocolate for grating
Line the base and two sides of a 20cm square cake tin with a long piece of baking paper making sure it has an overhang on opposite sides. These "handles" help lift the finished slice from the tin.
Preheat the oven to 170°C fan bake.
Prick each sheet of pastry with a fork. Place one piece on a lined, flat baking tray.
Place another sheet of baking paper over the top and cover with a 2nd baking tray. Bake for about 20 minutes until a good golden colour. Transfer to a cooling rack and repeat with the 2nd sheet of pastry.
Place the cake tin on top of each piece and using the tip of a sharp knife, carefully trim them to a 20cm square, reserving the scrapes for decoration. Place one sheet in the base of the tin and set the other aside.
Custard: Put the milk, cream, sugar, butter, vanilla and salt in a medium saucepan and heat until just below boiling point.
Whisk the egg yolks and cornflour together in a heatproof bowl until smooth.
Gradually whisk in the hot milk mixture then tip back into the saucepan.
Place over a medium/low heat and cook for 5 minutes, slowly bringing it to just blow boiling point and whisking constantly. The custard should be thick and smooth. Take off the heat and stir in the chocolate. Pour the hot custard over the pastry base and top with the second sheet and gently press it onto the custard. Cool then cover and refrigerate until the custard is set, about 8 hours or overnight if desired.
Icing: Combine the cream, water and vanilla together then stir into the icing sugar, adding a tiny bit more water if necessary to make a thick but spreadable icing.
To finish: Spread the icing over the top layer of pastry. Crush some of the pastry trimmings and sprinkle over the top of the wet icing then grate over a layer of chocolate. When the icing is set, use the baking paper to help lift the slice from the tin. Use a sharp serrated knife to cut into squares. Store the slice in a covered container in the fridge. Makes 12 squares