Make a simple syrup by mixing 3 oz. of water and 3 oz sugar. Bring to a boil until the sugar has dissolved. Remove from heat and cool completely.
Prepare a freezer proof tray and add Gin, syrup, lime juice and prosecco into tray. Stir to combine.
Freeze for approximately 2 hours or until the mix is slushy. Remove from freezer and stir with a fork. Place back in the freezer for another 2 hours.
When ready to serve, drag a fork through the mix again. Serve immediately.