Chocolate tart

melted butter for greasing
250g pkt chocolate coated biscuits
80g butter melted, cooled
300ml thickened cream
300g dark chocolate finely chopped
extra 40g butter, chopped
2 tbsp frangelico
1 tbsp icing sugar
1 tbsp cocoa or drinking chocolate

1. Brush a 20cm square fluted flan tin with butter. Put biscuits in a food processor and process until finely chopped. Transfer to a bowl. Add butter and stir until well combined. Press into base and sides. Refrigerate 30 minutes or until firm.
2. Put cream in a heavy based pan on medium heat. When cream just comes to the bil, remove from heat. Add chocolate and extra butter and stir until mixture is smooth. Add liqueur and stir until well combined. Pour into pie shell and refrigerate for 3 hours or until filling is set.
3. Remove pie from tin and transfer to a serving plate, dust with combined icing sugar/cocoa mixture.