Preheat the oven to 225 degrees F. Line a cookie sheet with parchment. Beat the egg whites and cream of tartar until very soft peaks form. Slowly add the sugar, beating constantly. Keep beating until the mixture is thick and glossy and stiff peaks form. Spoon the meringue into a piping bag fitted with a small plain tip about a 1/3--inch in diameter. Pipe a 1-inch round, 1/2-inch tall circle on the baking tray. Pipe a ring of meringue on the outer edges the circle. Repeat with the remaining meringue. Bake for 20 minutes. Turn the heat off and let the meringues cool completely in the oven. Whip the whipping cream with the icing sugar until stiff peaks form. Pipe the whipping cream into the centre of each meringue. Top each with a mandarin orange segment and a sprig of mint.
Note: The meringues, unfilled, could be made a few days in advance. Store in a single layer in an air-tight container at room temperature.