To make glaze: Blend the sugar, cornflour and salt; stir in apple juice. Cook over medium heat, stirring constantly until smooth and thick. Allow to cool for 10 minutes.
Spread a small quantity of the glaze over the bottoms of the tart shells. Arrange strawberries over the glaze, slicing if necessary to fit into the tarts. Spoon remaining glaze carefully over the berries, covering them well. Chill for 2 to 4 hours. Serve garnished with whipped cream or custard if desired.