Pastry: Lightly spoon flour into measuring cups and level with a knife. Combine flour and next 3 ingredients in a food processor; pulse two times. Add butter to flour mixture; pulse 4 to 5 times or til mixture resembles coarse meal. With processor on, slowly add buttermilk through chute; process just until dough forms into a ball. Gently press dough into a 4" circle on plastic wrap; cover. Chill 30 minute.
Preheat oven to 350.
Unwrap dough and place on a sheet of parchment. Roll dough into a 15" circle. Place dough and parchment on a baking sheet.
To prepare filling, combine berries and next 3 ingredients in a medium bowl; toss gently to coat. Arrange berry mixture in center of dough, leaving a 2" border. Fold edges of dough toward center, pressing gently to seal (dough will only partially cover berries).
Combine skim milk with the egg white in a small bowl. Brush dough with milk mixture and sprinkle with turbinado sugar. Bake at 350 for 1 hour or until pastry is golden. Let stand 30 min; cut into wedges.