Preheat the oven to 400 degrees F. Using a mixer fitted with a paddle attachment, combine the flour, baking powder, salt, and black pepper in a large bowl on low speed. With the mixer running, gradually add the cubes of butter until the mixture is crumbly and studded with flour-butter bits about the size of small peas. Add the grated cheese and mix until just blended. (This can also be done by hand: In a large bowl, stir together the flour, baking powder, salt, and pepper. Gradually cut in the butter with a pastry blender or two knives until the mixture resembles small peas. Stir in the cheese.)
Add the green onions, bacon, and ¾ C of the buttermilk to the flour and cheese mixture. Mix by hand just until all the ingredients are incorporated. If the dough is too dry to hold together, use the remaining buttermilk, adding 1 Tbsp at a time, until the dough is pliable and can be formed into a ball. Stir as lightly and as little as possible to ensure a light-textured scone. Remove the dough from the bowl and place it on a lightly floured flat surface. Pat the dough into a ball. Using a well-floured rolling pin, flatten the dough into a circle about 8 inches wide and ½ inch thick. Cut the dough into 8 to 10 equal wedges, depending on the size scone you prefer.
Whisk the egg and water in a small mixing bowl to combine. Brush each wedge with the egg wash. Place the scones on an ungreased baking sheet and bake for 18 to 20 minutes, or until golden brown and no longer sticky in the middle. Serve warm.
My customers demand a peppery bacon-cheddar scone. If you’re a freshly ground pepper aficionado, too, add at least 1 more teaspoon to the recipe. (I often use a total of 1 Tbsp of pepper and I prefer coarsely ground.) To give these a Texas twist, I add 2 chopped and seeded fresh jalapeno peppers.