'Viennetta' Slice

Step 1: Grease a 18 x 28cm slice pan. Line the base and 2 long sides with baking paper, allowing the paper to overhang the long sides.

Step 2: Place the biscuits in a food processor and process until resembles fine crumbs and then add the butter and process until combined and now spoon into prepared pan and using a flat-bottomed, straight-sided glass to press and evenly spread the mixture over the base and then place in the fridge for 30 minutes to chill.

Step 3: Place 60 ml (1/4 cup) water in a small heatproof bowl and sprinkle with the gelatine and stir until well combined and then place the bowl inside a larger heatproof bowl and pour boiling water into the larger bowl until it reaches halfway up the side of the smaller bowl and then set aside, stirring occasionally, for 5 minutes or until the gelatine dissolves.

Step 4: Meanwhile, use electric beaters to beat the cream cheese in a large bowl until smooth and add the sugar and vanilla and beat until combined.

Step 5: Remove and reserve 2 cupfuls of the mixture.

Step 6: Add the gelatine to the remaining cream cheese mixture and beat until combined.

Step 7: Combine the dark chocolate and oil in a bowl and spread half the cream cheese mixture over the biscuit base and drizzle over half the chocolate mixture to cover.

Step 8: Place dollops of the remaining cream cheese mixture over the chocolate layer and carefully spread to create another layer and drizzle over the remaining chocolate mixture to cover.

Step 9: Use electric beaters to beat the cream and reserved cream cheese mixture in a bowl until the mixture thickens slightly and then spoon into a piping bag fitted with a ruffle nozzle (see note) and pipe the cream cheese mixture over the top of the slice and dust with the cocoa.

Step 10: Place in the fridge for 4 hours or until the cheesecake is firm and set.

Step 11: Dust with extra cocoa and shaved chocolate, if using, just before serving.