Preheat oven to 200oC. Draw a 24cm (diameter) circle on a sheet of baking paper. Place, pencil-side down, on a baking tray. Dust lightly with 1 teaspoon cornflour
Using an electric mixer, beat eggwhites and cream of tartar in a large bowl until soft peaks form. Add sugar, 1 tablespoon at a time, beating constantly until thick and glossy. Add remaining 3 teaspoons cornflour with the last tablespoon of sugar. Fold through vanilla and vinegar.
Spoon meringue onto baking paper. Shape into a circle, using the pencil mark as a guide. Reduce oven to 100oC. Bake for 1 1/4 to 1 1/2 hours or until dry and crisp. Turn off oven and open oven door. Cool completely in oven (pavlova may sink during cooling).
Crumble meringue into a large serving bowl. Stir through cream and strawberries. Sprinkle with mint leaves and serve immediately.