Put the sugar and
cardamom pods in a heavy-based saucepan, pour in the
water and heat gently, stirring occasionally, until
the sugar has dissolved.
Increase the heat and bring
to the boil, then boil for 7 minutes without
stirring. Remove from the heat and leave to cool.
Meanwhile, peel the mangoes and remove as much flesh
as possible from the stones. Put the flesh in a
blender or food processor and work to a puree, then
pour into a shallow container.
Strain the cooled
syrup into the mango puree and stir well to mix.
Freeze uncovered for 3 hours.
Turn the mango
mixture into a bowl and beat with a fork until
broken up.
Whisk the egg whites until stiff. Fold
the egg whites into the mango mixture until evenly
mixed, then return the mixture to the container.
Cover and freeze
overnight. Transfer to the refrigerator for 20
minutes before serving.