Place the frozen blackberries in a small bowl and toss with 1 Tb of the flour. Put the bowl back in the freezer or you will end up with mush instead of berries.
In a large mixing bowl, combine the remaining flour, baking powder, salt, & sugar. Cut 6 tablespoons of the butter into small pieces and then "cut" the butter into the flour mixture with a pastry blender or two knives. The butter should not have any pieces larger than a pea.
Measure your half & half and then stir the vanilla into it. Pour the mixture into the center of your dry ingredients and stir it together until just combined.
Take the blackberries out of the freezer and, with floured hands, gently work the blackberries into the dough.
Turn dough out onto a floured surface and pat it into a square-ish shape, about 3/4 inch thick. With a knife, cut the dough in half each way, making 4 squares. Cut each square diagonally making 8 triangles. Place the triangles onto a baking sheet or stone. (I have a well-seasoned baking stone, you may want to line your stone/sheet with parchment paper.)
Take the remaining 1/2 Tb of cold butter and cut it into 8 tiny pieces. Place one piece on top of each scone.
Bake for about 15-17 minutes, until scones are just turning golden brown.
Remove them to a cooling rack that has been placed over a sheet of parchment paper or foil (for easy clean-up).
For the Glaze:
Whisk together the powdered sugar and lemon juice until smooth. Drizzle it over the top of the scones.Enjoy!