Combine chopped peach, lime juice and sugar in a saucepan over low heat. Cook, stirring occasionally, for 5-7 mins or until peach is very tender. Remove from heat. Transfer to a blender. Blend until smooth. Place in the fridge to chill.
Divide extra peach and raspberries among serving glasses. Combine peach puree and gin, if using, in a jug. Pour evenly among the glasses. Top with ice, mineral water and mint. (If not using gin, add extra mineral water or soda water.)