Cook the bacon: In a skillet over medium heat, cook bacon until crisp. Drain on paper towels and let cool.
Crumble into small pieces and set aside. Reserve a tablespoon of bacon fat if you’d like to brush the tops later.
Preheat and prep: Heat oven to 400°F (200°C). Line a baking sheet with parchment paper.
Chill the sheet in the fridge while you make the dough to help keep the scones cold.
Mix dry ingredients: In a large bowl, whisk 2 1/2 cups all-purpose flour, 1 tablespoon baking powder, 1/2 teaspoon baking soda, 1 tablespoon sugar, 1 teaspoon kosher salt, and 1/2 teaspoon black pepper.
Cut in the butter: Add 1/2 cup (1 stick) cold unsalted butter, cubed. Using a pastry cutter or your fingertips, work the butter into the flour until pea-sized bits remain. Keep it a little chunky—those butter pockets create flakiness.
Fold in add-ins: Stir in 1 cup shredded sharp cheddar, the crumbled bacon, and 2 tablespoons finely sliced chives or green onions.
Add wet ingredients: In a small bowl, whisk 3/4 cup cold buttermilk with 1 large egg.
Pour over the flour mixture. Use a fork to gently combine until a shaggy dough forms. If it’s dry, add 1–2 more tablespoons buttermilk.
Bring it together: Turn the dough onto a lightly floured surface.
Gently press and fold it over itself 3–4 times to bring it together. Avoid kneading; you want to keep the butter cold and the dough tender.
Shape: Pat the dough into a round about 1 inch thick and 7–8 inches across. Use a sharp knife or bench scraper to cut into 8 wedges.
Transfer to the chilled, lined baking sheet, spacing slightly apart.
Top and chill briefly: For glossy tops, whisk 1 egg with 1 tablespoon heavy cream and brush lightly over the scones. Alternatively, brush with a little reserved bacon fat for extra flavor. Sprinkle a pinch of cheddar on each.
Bake: Bake 15–18 minutes, until golden on the edges and set in the center.
They should feel firm but not hard. If your oven runs cool, give them another minute or two.
Cool slightly and serve: Let scones rest on the sheet for 5 minutes, then transfer to a rack. Serve warm with butter, hot sauce, or a fried egg on the side.