Roughly break the plain biscuits into small pieces.
Melt the dark chocolate. Set aside.
Whisk softened butter, icing sugar, vanilla essence and liquor until smooth.
Add a pinch of salt.
Add melted chocolate and mix.
Add crushed biscuits, pistachios, and cocoa powder and mix together.
Shape into a log with baking paper and wrap. Refrigerate for 4h.
Dust with icing sugar before serving.
