Tip the raspberries, wine and sugar into a blender and blitz until smooth (this can also be done in a large jug with a hand blender). Push the liquid through a sieve to get rid of some of the pips, then churn in an ice-cream machine until the texture of soft sorbet.
Transfer to a freezable container and freeze for at least 4 hrs. If you don't have an ice-cream machine, freeze the liquid until it starts to become icy, then mash the ice crystals with a fork until slushy. Repeat 3 or 4 times until you have the texture of sorbet.
To serve, toss the peaches with the mint and serve alongside bowls of the scooped slush.