Preheat oven to 100C. line a baking tray with baking paper. Draw a 20 cm circle on the paper and turn over.
Use an electric mixer to whisk the egg whites and cream of tartar in a clean, dry bowl until firm peaks form.
Gradually add the sugar, 1 tablespoon at a time, whisking well after each addition until the sugar dissolves and the mixture is thick and glossy. Add the cornflour. Stir until just combined.
Use a large metal spoon to spoon the mixture onto the lined tray. Use a palette knife to shape into a disc, using the circle as a guide.
Bake for 1 1/2 hours or until pavlova is dry to the touch. Turn off the oven . Leave the pavlova in the oven , with the door ajar, for 2 hours to cool completely.
Use an electric mixer to whisk icing sugar and cream.