Heat the milk with 1/2 cup sugar.
Add cornflour mixed with the cold milk.
Cook till well blended and smooth.
Add vanilla essence and gelatine and heat through.
In a deep bowl, arrange 6 biscuits at the base and the rest along the sides.
Mix mango pieces with the milk mixture leaving some for garnishing, and pour into the biscuit case.
Chill till set.
Whisk cream and powdered sugar and add remaining mango pieces.
Pour over the pudding and chill completely.
Remove just before serving.