Blend biscuits into a fine powder. Mix with melted butter and press firmly into the bottom of a 20–22 cm springform pan. Chill for 20 minutes.
Heat 100 ml cream until just simmering. Pour over chopped chocolate, let sit 1 minute, then stir until smooth. Cool slightly.
Whip the remaining 150 ml cream to soft peaks, then gently fold it into the chocolate mixture. Spread over the chilled biscuit base. Refrigerate 30 minutes to set.
Whip cream cheese with icing sugar and vanilla. In another bowl, whip the single cream until stiff peaks form, then fold into the cheese mixture. Spread this layer over the mousse and smooth the top. Chill for at least 4 hours or overnight.
Heat cream to a gentle simmer, pour over chopped chocolate, rest 1 minute, then stir until smooth. Add butter for shine. Let cool slightly, then pour over the set cheesecake. Chill again 30 minutes before serving.
