Line the base of a 22cm-diameter round springform cake tin with baking paper.
To make the Biscuit Base, blitz the biscuits and cocoa in a food processor.
Add the butter and pulse to combine.
Press into the prepared tin and refrigerate until needed.
To make the cheesecake filling, combine the chocolate and ½ cup of the cream in a medium bowl. Place over a pan of simmering water or microwave in 20–30 second bursts, stirring between bursts, until melted and smooth. Set aside.
Place the cream cheese in a mixer or large bowl and beat until smooth.
Add the icing sugar and the chocolate mixture and beat on a low speed until combined.
In a separate bowl, whip the remaining cream until stiff peaks form.
Fold the cream cheese mixture into the whipped cream on a low speed.
Spread over the prepared base and refrigerate for 6 hours or overnight until set.
To serve, dust with cocoa and decorate with whipped cream and flowers if desired.
