125g butter, plus extra for greasing
120g dark chocolate
3 Tbs brown sugar
2 Tbs raw cocoa powder
120g digestive biscuits
50g desiccated coconut
700mL full cream milk
1 vanilla bean
50g corn flour
2 egg yolks
250g butter, softened
100g milk chocolate
100g dark chocolate
2 Tbs canola oil
4 Tbs desiccated coconut for sprinkling
Butter a 22cm square cake tin and line with baking paper.
Grate chocolate and transfer to a small saucepan along with butter, brown sugar and cocoa. Gently heat to melt, stirring continuously.
Place biscuits inside a resealable plastic bag and pound them to fine crumbs with a rolling pin. Chop walnuts, thoroughly combine chocolate mixture, biscuit crumbs, chopped walnuts and coconut in a large mixing bowl.
Transfer mixture to cake tin, press down firmly with your hands and refrigerate for 30 minutes.
Heat milk in a saucepan, split vanilla bean lengthwise and scrape out seeds. Add to milk and stir briefly; set aside for 15 minutes to infuse flavour.
Whisk corn flour, sugar, eggs and yolks together in a large bowl.
Bring milk to boil briefly, add 100mL of hot milk to egg mixture and whisk to combine.
Pour egg mixture into hot milk, stirring continuously for another 2 minutes. Remove the pan from heat and leave custard to cool.
Beat butter until light and creamy, gradually whisk into cooled custard. Spread custard evenly over chocolate base and refrigerate for 2 hours.
Finely chop milk and dark chocolate. Melt together in microwave with canola oil. Quickly spread topping over chilled custard layer and sprinkle with coconut.
Refrigerate for at least 6 hours. Lift out of tin with baking paper and cut into small squares to serve.