Mix dry ingredients in a large bowl. Add in your cold, cubed butter. Work it into the flour with your fingers using a finger snapping motion. The mixture should resemble coarse crumbs with butter pieces no larger than the size of peas.
Stir in nuts, chips, herbs, fruit, or other add-ins into dry ingredients now, before adding your buttermilk.
Whisk together the buttermilk, egg, and vanilla extract, if using. Pour into the flour and butter mixture and begin mixing. Save about a tablespoon of the liquid to brush the tops of your scones.
Mix together until you have a cohesive shaggy dough with just a little bit of dry ingredients left on the bottom. If you have a lot of dry left, add another tablespoon of buttermilk and keep mixing.
Dump the dough onto a lightly floured surface and use your hands and/or a bench scraper to bring the dough together into a large square.
Use your hands, or the bench scraper, to fold the dough over onto itself two or three times. Gently using your hands to flatten it out between folds.
Shape into a disk about 6 to 8 inches across and use a knife to cut into eight wedges.
Place the wedges on a parchment paper lined large sheet pan and place into the freezer or refrigerator to chill while you preheat your oven to 400°F.
Brush your chilled scone wedges with the leftover buttermilk and egg mixture from the bottom of the measuring cup, or with an egg wash consisting of an egg whisk with 1 tablespoon of water.
If desired, sprinkle the tops of your scones with a little bit of sparkling sugar. Bake at 400° for 18 to 22 minutes, or until golden brown.
Allow the scones to cool for 15 minutes before glazing or eating.