Buttermilk Panna Cotta with Blackberry Sauce

In cup, evenly sprinkle gelatin over 1/4 cup water. Let stand 2 minutes to allow gelatin to absorb liquid and soften. In 3-quart saucepan, heat 1/2 cup buttermilk and 1/2 cup sugar on medium 2 to 3 minutes or until sugar dissolves, stirring occasionally. Reduce heat to low; whisk in gelatin. Cook 1 to 2 minutes or until gelatin dissolves, stirring. Remove saucepan from heat; stir in 2 1/4 cups buttermilk. Pour buttermilk mixture into eight 4-ounce ramekins or 6-ounce custard cups. Place ramekins in jelly-roll pan for easier handling. Cover pan with plastic wrap, and refrigerate panna cotta at least 4 hours or overnight, until well chilled and set. Reserve 1/3 cup blackberries for garnish. In blender, puree remaining blackberries with lemon juice, 2 tablespoons water, and remaining 4 teaspoons sugar. Pour puree through sieve set over small bowl, stirring constantly to press out fruit sauce; discard seeds. Cover and refrigerate sauce if not serving right away. To unmold panna cotta, run tip of knife around edge of each ramekin. With hand, sharply tap side of each ramekin to break seal; invert onto 8 dessert plates. Spoon sauce around each panna cotta. Garnish with reserved berries.