- With the rack in the middle position, preheat the oven to 400°F (200°C). Line a baking sheet with a silicone mat or parchment paper.
- In a large bowl, whisk together the flour, baking powder, sugar, pepper flakes and salt. Using a pastry blender, cut the butter into the flour until the butter forms pea-sized pieces. Add the buttermilk, cheese, bacon and chives. Using your hands, combine until just moistened.
- On a lightly floured surface, using your hands or a rolling pin, shape the dough into a 9-inch (23 cm) square. Cut into 9 squares. Using a spatula, evenly space the squares on the prepared sheet. Freeze the scones at this step, if desired.
- In a small bowl, combine the egg yolk and water. Brush the scones with the egg wash.
- Bake for 16 to 20 minutes or until golden brown. Let cool. The bacon, cheddar and chive scones are best enjoyed the same day.
The scones freeze well unbaked.