Mix the Champagne, water, and sugar in a medium nonreactive saucepan, bring to a boil. Add the raspberries, remove from the heat, and cover. Let stand for 10 minutes. Pass the mixture through a food mill with a fine disk, or press it firmly through a mesh strainer with a flexible rubber spatula. Discard the seeds.
Chill the mixture thoroughly, then freeze it in your ice cream maker according their instructions.
Recipe from The Perfect Scoop