Bring the water to the boil with the sugar, add the chopped peppermint and the zest of the organic lime. Let it steep for fifteen minutes on a low heat. Then take it off the stove and let it cool down.
Pour through a sieve, mix with the lime juice and pour over well-chilled mineral water. Serve garnished with a slice of lime, a little peppermint and a few blueberries.