Ingredients: 375 g flour, 50 g sugar, 15 g baking powder, 5 g salt, 170 g cold butter cubed, 180 g cold buttermilk, 1 egg for wash.
Whisk dry ingredients. Cut in butter until pieces are pea-sized. Add buttermilk and mix just until it comes together.
Turn onto a floured surface. Fold in thirds like a letter, twice, for layers. Pat to 1 inch thick.
Cut into wedges or rounds. Freeze on the tray for 15 minutes — this is the secret to height in the oven.
Brush with egg wash. Bake at 425°F for 18–20 minutes until deeply golden. Eat warm.