For the raspberry splash with lime-mint granité, bring the water, sugar and lime juice to the boil until the sugar has dissolved.
Finely chop the mint leaves and mix with the sugar water. Transfer to a small plastic bowl and freeze in the freezer for at least 4 hours. During this time, keep stirring well to make a grainy granité mixture. This can then either be scraped with a knife or formed into balls with an ice cream scoop.
Carefully sort out the raspberries and divide them among 4 glasses. Place a scoop or some scraped lime-mint granité on top of the fruit and top with sparkling wine or Prosecco.
Serve the raspberry spritzer with lime-mint granité.