Preheat the oven to 425 degrees.
In a bowl, whisk together flour, baking powder, sugar, and salt.
Cut in butter with a pastry blender or two knives until the mixture resembles coarse crumbs.
Stir in ⅔ cup half-and-half and vanilla extract until just moistened.
Gently fold in fresh blackberries.
On a lightly floured surface, knead dough gently 5 to 10 times.
Pat into a 1-inch-thick round.
Cut into 8 wedges; place on a parchment-lined baking sheet, 2 inches apart.
Brush tops with 1 Tablespoon half-and-half, then sprinkle each scone top with sugar.
Bake until golden brown, 12 to 15 minutes.
Cool on wire rack.