Preparation Place frozen berries in large bowl. Sprinkle sugar over berries; let stand until berries are just thawed but still cold, about 1 hour. Using fork, coarsely mash berries. (Can be made 4 hours ahead. Cover and refrigerate.) Spoon sorbet into dessert glasses. Top with blackberry sauce and serve.
Preparation Place frozen berries in large bowl. Sprinkle sugar over berries; let stand until berries are just thawed but still cold, about 1 hour. Using fork, coarsely mash berries. (Can be made 4 hours ahead. Cover and refrigerate.) Spoon sorbet into dessert glasses. Top with blackberry sauce and serve.