Makes 2 to 4 servings
Hands-on time: about 10 minutes
Total preparation time: about 10 minutes plus freezing
½ cup white grape juice
1 cup seedless red or green grapes
1 cup buttermilk
1½ to 2 tablespoons sugar or to taste
½ teaspoon vanilla extract
Six to eight hours before preparing, freeze the grape juice in an ice cube tray to make about four cubes. To prepare frappé, combine grapes, buttermilk, 1½ tablespoons sugar, and the vanilla in a blender.
Blend until very smooth. Add grape juice cubes and blend until smooth. Taste and blend in additional sugar, if necessary. Strain if desired and divide into chilled glasses.