Preheat your oven to 400°F (200°C) and prepare a baking sheet with parchment paper.

In a large bowl, whisk together the flour, sugar, baking powder, and salt.

Add in the chilled, diced butter and blend with a pastry cutter until the mixture resembles coarse crumbs.

Gently fold in the blueberries.

In a separate bowl, combine the buttermilk and vanilla extract.

Add the wet ingredients to the dry ingredients and mix until just combined.

Turn the dough out onto a floured surface and knead lightly. Roll out to a 1-inch thickness and cut into triangles or circles.

Transfer the scones to the prepared baking sheet and brush the tops with the beaten egg.

Sprinkle with additional sugar if desired.

Bake for 18-20 minutes or until golden brown.

Serve warm or let cool on a wire rack.