Preheat oven to 425°F. Line a large baking sheet with parchment paper. Set aside.
Set out a sheet of parchment paper. Using the fine edge of a grater, grate butter onto the parchment paper. Place it in the freezer while you prepare the remaining ingredients.
In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt.
Remove grated butter from the freezer. Using a fork, incorporate it into the dry ingredients.
Add in the chopped white chocolate.
In a separate bowl, whisk together the heavy cream, eggs, and vanilla.
Add the wet ingredients to the dry ingredients. Mix until just combined.
Gently mix in the frozen blackberries, folding the dough 3-4 times. There will be some bleeding into the dough and that is okay!
On the lined baking sheet, shape the dough into a circle, about ¾-inch thick. Add a bit of flour to your hands to prevent sticking.
Using a bench scraper or large knife, cut the dough into 6-8 wedges (I cut them into 8), gently separating the edges of each scone, creating a ½-inch space between each.
Brush scones with heavy whipping cream, making sure to cover all exposed edges. Sprinkle with turbinado sugar.
Bake the scones for 18-23 minutes, or until golden brown.