If using fresh berries, flash freeze them on a baking sheet lined with parchment paper for about one hour or until the berries have hardened. If your berries are already frozen, skip to step 2.

Preheat the oven to 375 degrees. Line two baking sheets with parchment paper and set aside.

Sprinkle the cubed butter over the dry ingredients, and cut in with a pastry cutter until the dough is crumbly throughout.

Stir the vanilla extract into the buttermilk, then stir this mixture into the dry ingredients just until blended. Fold the frozen berries into the dough, being careful not to smash them. The dough will still be crumbly, which is okay. Do not over mix.

Lightly flour the work surface, and then turn the dough out onto it. Flatten the dough out into a circle that's about 1 ½ inches thick. Using a bench scraper or sharp knife, cut the dough into 8 wedges.

Place the scones on the prepared baking sheets, 4 to a sheet. Make the egg wash by mixing together the egg and water, and brush this mixture lightly on the top of each scone. Sprinkle the remaining sugar over the tops.

Bake at 375 degrees for 15 to 20 minutes or until golden brown. Cool for 5 minutes before serving.