Preheat oven to 350 degrees. Butter and flour a nine by nine inch baking pan.
In a large bowl whisk together all the dry ingredients. Cut in the butter pieces with a pastry cutter, two forks or your hands until mixture is crumbly. (Or you could also use a food processor.) Set aside 1/2 cup of mixture.
In a small bowl whisk together egg, milk and vanilla and add to large bowl of dry mixture, gently folding it in just until combined.
Pour the batter into prepared pan and evenly distribute berries on top. Top berries with reserved flour mixture. Bake for 45 minutes or until a toothpick inserted in the center comes out clean.