Preheat your oven to 400°F. Line a large baking sheet with parchment paper, and set aside.
In a large bowl, combine your flour, sugar, baking powder, baking soda, and salt. Whisk together to combine.
Add your cubed butter to the dry ingredients. Using a fork or pastry cutter, cut the butter into the dry ingredients until you're left with mixture that resembles coarse breadcrumbs (a few large pieces of butter are okay). Add your blueberries (or other add-ins) and gently mix to coat in the dry ingredients, and set aside.
In a separate medium bowl, combine your buttermilk, egg, and vanilla extract. Whisk your wet ingredients together to incorporate. Pour the wet ingredients over the dry ingredients. Mix everything together until a rough dough starts to form.
Turn your dough onto a floured work surface and flour the top to keep it from sticking. Using your hands, press and flatten the dough into a circle that's about 3/4 inch thick and about 9 inches in diameter. Using a large knife, cut the circle into 8 equal sized wedges. Transfer the wedges to your parchment lined baking sheet, leaving about 1 inch of space in between each scone.
Bake the scones in the center of your preheated 400°F oven for 15 to 20 minutes, or until golden brown and puffed. Cool slightly before serving. Scones are best enjoyed warm. Dust with powdered sugar, top with an icing, or serve plain!