1Preheat oven to 220 C. Lightly grease a 23 cm square cake pan. Line base and sides with baking paper, and extend paper 2 cm over edge.
2Place pastry sheet on trays. Bake 10 to 12 mins, until puffed and golden. Cover with a tea towel. Gently flatten pastry with hands.
3Using pan as a guide, trim pastry sheets to fit. Line base of pan with one sheet of pastry.
4In a medium saucepan, combine sugar, cornflour, custard powder and cocoa. Pour in milk and cream, stirring until smooth.
5Remove from heat. Stir in chocolate and butter, then yolks and vanilla. Pour custard into pan over pastry, smoothing surface. Top with remaining pastry sheet. Press down gently. Chill 1 hour.
6CHOCOLATE GANACHE Simmer cream in a saucepan. Place chocolate in a heatproof bowl and pour cream over. Stir until smooth. Spread over pastry, then decorate with Snickers.
Photo: Rob Shaw/BauerSyndication.com.au