In a pestle and mortar, bash most of the mint leaves (reserving the remainder to decorate) with the finely grated lime zest. Add the sugar and a good lug of cachaça. Mix gently in the mortar and pestle, add the lime juice, taste and add more sugar if you think you need to.
Toss the fruit together in a bowl with a little of the mint and lime mixture, then spread it all out on a big plate. Spoon the rest of the mint and lime mixture over the top. Decorate with the remaining mint before serving.