Combine 3/4 cup water and sugar in a small saucepan; bring to a boil, stirring until sugar melts. Remove from heat, and cool completely.

Position knife blade in food processor bowl; add raspberries and remaining 1/4 cup water. Process until smooth. Strain and discard seeds.

Combine sugar-water mixture, raspberry puree, and champagne. Pour mixture into the freezer can of an ice-cream freezer, and freeze according to the manufacturer's directions. Spoon into a freezer-safe container; cover and freeze (ripen) 1 hour. Yield: 4 cups (serving size: 1/2 cup).