Preheat oven to 150°C (300°F). Place the eggwhite in the bowl of an electric mixer and whisk until stiff peaks form. Gradually add the sugar, whisking well, until the mixture is stiff and glossy. Add the cornflour, vinegar and rosewater and whisk until just combined. Shape the mixture into 16 x 8cm rounds on baking trays lined with non-stick baking paper. Reduce oven to 120°C (300°F) and bake for 35 minutes. Turn the oven off and allow the pavlova rounds to cool completely in the oven. Whisk the cream until soft peaks form and serve with the pavlova rounds and blueberries. Makes 16.