For the scones:
3 cups all-purpose flour
1 tbsp. baking powder
1 tsp. salt
1-2 tsp. ground black pepper (depending on your preference)
8 tbsp. cold unsalted butter, cut into small cubes
1½ cups grated cheddar cheese
4 green onions, thinly slices
10 slices bacon, cooked and chopped or crumbled into small pieces
1 cup buttermilk (plus up to ½ cup extra, if needed)
For the egg wash:
1 large egg
2 tbsp. water
Preheat the oven to 400˚ F. In the bowl of an electric mixer fitted with the paddle attachment, combine the flour, baking powder, salt and black pepper; mix briefly to combine. Add the cubes of butter and mix on low speed until the mixture is crumbly and the butter pieces are about the size of small peas. (Alternatively, this can be done in a regular mixing bowl, using a pastry blender or two knives to cut the butter into the dry ingredients.) Add in the grated cheese and mix just until incorporated.
Mix in the green onions, bacon, and 1 cup of the buttermilk into the flour-butter mixture. Stir by hand just until all the ingredients are incorporated. If the dough is too dry to come together, mix in the remaining buttermilk a tablespoon or two at a time until the dough can be formed into a ball. Transfer the dough to a lightly floured surface and pat the dough into an 8-inch disk. Slice the dough into 8 to 10 wedges.
In a small bowl combine the egg and water and whisk together. Brush each wedge lightly with the egg wash. Transfer the scones to an ungreased baking sheet. Bake for 18-20 minutes, or until golden brown and a toothpick inserted in the center comes out clean.