Pre-heat oven to 120°C (100°C fan-forced). Line a large baking tray with baking paper, drawing a 20cm circle on the paper.
Place egg whites and cream of tartar into the bowl of an electric mixer. Beat until firm peaks have formed. Gradually add sugar a little at a time, until all has been incorporated. Continue beating for 2 minutes once all of the sugar has been added.
Reduce mixer to slow speed and add cornflour, mixing until just combined. Spoon mixture onto baking paper and spread within the circle. Bake for 1½ hours and turn oven off. Leave pavlova to cool in the oven. Keep in a sealed container once cooled prior to decorating and serving.
Use an electric mixer to whisk the cream and icing sugar in a medium bowl until firm peaks form. Spoon cream onto the top of pavlova. Decorate pavlova with berries and shaved chocolate.