In bowl, combine all dry ingredients and whisk together. Using pastry blender or 2 knives, cut in cold butter until mixture resembles coarse crumbs.
In separate bowl, whisk buttermilk and egg and pour over flour mixture and stir with form to make soft dough. With lightly floured hands and on floured surface, press dough into ball; knead gently 10 times. Pat into 10 x 7 inch rectangle and cut into 12 squares.
Place on parchment paper-lined or flour-dusted baking sheet. Bake in centre of 400 degree oven until golden (12-15 minutes).