In a medium mixing bowl, add the flour, granulated sugar, kosher salt, baking soda, and baking powder. Mix until well combined.

Toss in the cold, cubed butter and work it into the flour mixture until it resembles large pea-sized crumbs.

Gently fold in the fresh blueberries.

In a separate measuring cup, combine the buttermilk, egg, and vanilla extract. Beat until fully mixed.

Create a well in the center of the flour mixture and pour in the wet mixture, reserving about 2 tablespoons for egg wash. Fold gently until just combined.

Turn the dough onto a floured surface. Gently fold it over itself 2-3 times and shape into a circle about 1 ½ inches thick.

Cut the dough into 8 equal scones and place on a lined baking sheet.

Refrigerate or freeze the scones while preheating the oven to 400°F (200°C).

Brush the tops and sides with the reserved egg wash and sprinkle with turbinado sugar.

Bake for 23-24 minutes, or until golden brown and a toothpick comes out clean.

Cool completely on a wire rack.