Grease and line a 29cm x 19cm slice pan.
Combine butter, sugar and cocoa in a saucepan on medium heat. Cook, stirring often, for 5 minutes, until sugar dissolves. Transfer mixture to a bowl. Stir in coconut, egg, savoiardi and cranberries.
Press mixture into pan. Cover and refrigerate for 3 hours, until firm. Dust with drinking chocolate. Cut into squares. Serve.
