Preheat oven to 400 degrees F.

Combine and whisk flour, baking powder, salt, and black pepper in a large bowl.

Gradually add the small cubes of chilled butter, cutting them into the dry ingredients with a pastry cutter until mixture is crumbly and resembles the size of small peas.

Add the grated cheese, onions, and bacon and mix until just blended.

Add 3/4 cup buttermilk and stir gently until all ingredients are incorporated. If the dough is too dry to hold together, use the remaining buttermilk, one tablespoon at a time until the dough is pliable and can be formed into a ball. Stir as lightly as possible to ensure a light-textured scone.

Remove the dough from the bowl and place on a lightly floured surface, and pat the dough into a ball.

Using a floured rolling pin, flatten the dough into a circle, about 8 inches wide and 1/2 inch thick.

Cut the dough into 8 to 10 equal wedges and place on an ungreased baking sheet.

Whisk the egg and water in a small bowl. Using a pastry brush, brush each scone with the egg wash.

Bake for 18 to 20 minutes, or until golden brown and no longer sticky on top.

Best served warm out of the oven. (Note: You can make the dough the night before and place covered and unbaked scones in refrigerator overnight.)