1. Line baking sheet with parchment paper; trace six 3-inch circles on paper. Turn paper over; set aside.
2. In large bowl, beat egg whites with cream of tartar until soft peaks form. Beat in sugar, 2 tbsp at a time, until stiff glossy peaks form. Spoon meringue into piping bag fitted with ¾-inch plain tip. Pipe meringue to cover circles on prepared baking sheet.Pipe two more rings of meringue on top of outer edge to form walls of pavlovas.
3. Bake in centre of 250ºF oven until crisp with slightly soft centres, about 1 hour. Let cool on pan on rack. (Make ahead: Cover loosely with foil and let stand at room temperature for up to 1 day.)
1. Whip cream with sugar; gently fold in chopped strawberries. Spoon into pavlovas. For each pavlova, cut the top off of a strawberry, and slice in half. Place 2 halves on top of filling. Garnish with mint sprig.