Preheat oven 160°C (320°F). Place the butter and sugar in the bowl of an electric mixer and beat for 8–10 minutes or until light and creamy. Add the egg and vanilla and beat until well combined. Add the flour, cocoa, bicarbonate of soda and melted chocolate and beat until just combined. Fold through the extra chopped chocolate. Roll tablespoonfuls of the mixture into rounds.
Place on baking trays lined with non-stick baking paper, allowing room for the cookies to spread, and flatten slightly. Press the chopped candy canes into the tops of the cookies and bake for 12–15 minutes or until the edges are firm. Allow to cool on the trays. Makes 20.