Step 1

Line the base and 2 long sides of a 20cm x 20cm square cake tin with baking paper, allowing the sides to overhang. Line the base with half the lattice biscuits, cutting them to fit if necessary.

Step 2

Meanwhile, place the milk, cream and half the sugar in a medium saucepan. Use a small sharp knife to scrape the seeds from the vanilla bean into the pan. Place over medium-low heat and bring just to the boil. Remove from heat. Whisk the egg yolks, cornflour and remaining sugar in a medium bowl until smooth. Gradually whisk the hot milk mixture into the egg mixture until the custard thickens and coats the back of a wooden spoon. Return to pan. Place over medium-low heat and cook for 2-3 minutes until the custard is very thick.

Step 3

Pour the custard over the biscuit base and smooth the surface. Arrange the remaining biscuits on top, cutting to fit. Place in fridge for 2-3 hours or until set. Cut into slices and serve.