Combine 3/4 cup of blueberries and orange juice into a blender and puree
Pour into small sauce pan with sugar and cornstarch. Cook until very thick and cool.
Put 1/4 cup of blueberries into each tart. Completely cover with thickened cooled sauce.
Put spoon of whipped topping on top of each tart. Put a few berries on top of each tart as a garnish.