Mix sugar and water in a saucepan and heat it until the sugar has dissolved in the water (the water should be clear)
Wash the mints and mash it in your hand before adding to the saucepan along with the lime
Let the syrup boil under a lid for 10 min
Take the saucepan off of the heat and leave it for a few hours
Remove the mint leaves by passing the syrup through a thin cloth or tea filter
Pour the mint syrup into a bottle and store it in a cool place