Prep. Preheat the oven to 400˚F and line a baking sheet with parchment paper. Set aside.
Combine the dry ingredients and butter. In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt. Add in the butter pieces; cut in the butter using a pastry blender or a fork to form fine crumbs.
Add the wet ingredients and blueberries. Stir in the buttermilk, egg, and vanilla; mix just until combined. Using a spatula, fold in the blueberries.
Shape the dough. Turn out the dough onto the previously prepared baking sheet. Flour your hands and shape the dough into a circle. Using a sharp knife, cut the circle into 8 wedges. Spray the tops with cooking oil and sprinkle with turbinado sugar, if using.
Bake. Transfer the baking sheet to the oven and bake the scones for 20 to 23 minutes, or until golden on top.
Make the glaze. In the meantime, prepare the glaze by combining the powdered sugar, milk, and lemon juice in a mixing bowl; whisk until everything is completely incorporated and no lumps appear. Add more liquid if needed. For a thicker glaze, add more powdered sugar.
Finish and serve. Remove the scones from the oven and transfer them to a wire rack. Set aluminum foil under the wire rack to catch the glaze drippings. Drizzle the glaze over the blueberry scones. Serve.
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Notes
Make ahead: Prepare the scone dough and shape the scones, then cover and refrigerate them overnight. Bake them the next morning as directed.