In a small bowl, whisk together buttermilk, egg & vanilla; add to flour mixture. Fold in just until incorporated then carefully fold in blackberries. Place dough on parchment paper lined baking sheet. With lightly floured hands, pat dough into an 8-inch circle. Score into 8 wedges. Bake 20 minutes or until golden & test done. Cover lightly with foil if over browning before baked. Remove from oven to a cooling rack. Cool before glazing.