In a small bowl, whisk together corn starch, and both juices until well blended.
In a medium saucepan, bring the strawberries, sugar, and citrus juice and corn starch mixture to a boil. Stir gently and constantly with a large spoon.
Once the mixture has thickened, remove from the heat. Pour the topping into a heatproof bowl and allow to cool.
Store covered in the refrigerator until ready to use.