1 ½ x 200g packets lattice biscuits
2 x 400ml cans coconut milk
1 cup milk
300ml tub thickened cream
½ cup vanilla-flavoured custard powder
1/3 cup caster sugar
2 egg yolks
2 teaspoons vanilla extract
5 teaspoons powdered gelatine
2 cups icing sugar mixture
1 tablespoon desiccated coconut
Grease a 24cm square cake pan (base measures 20.5cm, with slopping sides). Line base and sides with baking paper, extending paper 3cm above pan edges.
Arrange 13 of the biscuits, glazed-side down and trimming to fit, over base of pan.
Set aside ¼ cup of the coconut milk in the fridge to make the icing.
Heat remaining coconut milk, milk and cream in a large saucepan over a medium heat, stirring until hot. (Do not boil.)
Whisk custard powder in a large bowl with sugar, yolks and vanilla until combined. Whisk in ½ cup hot milk mixture until smooth, then gradually whisk in remaining hot milk.
Strain back into same saucepan. Whisk over a high heat for about 6 minutes, or until boiling and thickened. Continue whisking for 1 minute. Remove custard from heat.
Sprinkle gelatine over 1/3 cup water in a small heatproof jug. Sit jug in a saucepan of simmering water. Stir until gelatine is dissolved. Whisk into hot custard.
Pour custard over biscuits in pan. Arrange 16 of the biscuits, glazed-side up and trimming to fit, over top, reserving remaining for another use. Refrigerate slice overnight.
To make icing, stir reserved ¼ cup coconut milk into icing sugar in a bowl. Stir in 1 to 2 teaspoons hot water to form a thick, spreadable consistency. Spread over slice. Sprinkle with coconut. Refrigerate until set.
To serve, lift slice from pan. Cut into squares.