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.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.