Mix the crushed digestive biscuits with melted butter and caster sugar until evenly coated.
Press firmly into a 20cm springform tin and chill for 20–30 minutes.
Melt the dark chocolate and allow it to cool slightly.
Beat the cream cheese with icing sugar until smooth.
Mix in the melted chocolate, orange zest, orange juice, vanilla extract, and soured cream.
Whip the double cream to soft peaks and gently fold it into the chocolate mixture.
Spread the filling evenly over the chilled biscuit base.
Refrigerate for at least 6 hours or overnight until fully set.
Decorate with chocolate curls, grated chocolate, whipped cream, and fresh orange zest before serving.