Puree grapes in a high-speed blender until very smooth. Transfer to a medium saucepan and bring to a simmer. Reduce heat to low and cook for 10 to 15 minutes or until reduced to 1 cup. Cover and refrigerate until well chilled. Stir into creamer and pour into the bowl of an ice cream maker. Freeze according to manufacturer’s directions. Transfer to a freezer-safe container; cover and freeze until firm.