1. Peel the mangos and scrape all the flesh away from the stones. Place the caster sugar, lime zest, lime juice and water in a pan and bring to the boil, simmering for 5 minutes. Skim any froth off the top of the liquid and leave to cool.
2. Place the cooled lime syrup and mango pieces into the Braun Multiquick 9 cordless large chopper accessory and blend until smooth.
3. Pour the mixture into a bowl and freeze for 3-4 hours until firm.
4. Take the sorbet out of the freezer and leave it to rest for 10 minutes so it is easier to spoon out.