2 cups all-purpose flour
2 tbsp. sugar
1½ tbsp. baking powder
½ tsp. salt
8 tbsp. cold unsalted butter, cut into small pieces
1 whole egg
1 egg yolk (optional)
Scant 1 cup buttermilk
¼ cup snipped fresh chives
Preheat the oven to 400˚ F. Line baking sheets with parchment paper or silicone baking mats. In a bowl, combine the flour, sugar, baking powder and salt. Whisk together to blend. Add the cold butter to the dry ingredients and, using a pastry cutter, cut the butter into the flour until the mixture resembles coarse meal and the largest butter pieces are the size of peas. (This can also be done in a food processor or stand mixer.)
Place the egg and egg yolk in a liquid measuring cup. Add enough buttermilk to measure a full 1 cup. Whisk in the snipped chives. Add the buttermilk mixture to the flour mixture and mix together gently just until the dough comes together and all the dry ingredients are absorbed.
Transfer the dough to a lightly floured work surface and pat into a disc that is ½-inch thick. Use a well-floured 3-inch round biscuit cutter and cut out dough rounds. Place finished rounds on the prepared baking sheets. Gently re-roll the excess dough and cut out additional biscuits. Bake until golden brown and fluffy, about 12-15 minutes. Remove from the oven and serve warm.