In a large bowl, whisk together flour, sugar, salt, and baking soda.
Cut in cold butter until the mixture looks like coarse crumbs. Stir in raisins if using.
In a small bowl, whisk egg yolk and buttermilk, then pour into the dry ingredients. Gently mix until combined.
Turn onto a lightly floured surface, knead briefly, and shape into a 4-inch circle. Tip: Add a little more flour if the dough is sticky.
Place on a baking sheet and score a ½-inch-deep “X” on top with a sharp knife.
Bake in a preheated oven for about 40 minutes, until golden and hollow-sounding when tapped on the bottom.Tip: If the top browns too quickly, cover with aluminum foil.
Let the bread cool slightly, then serve warm or at room temperature.
Notes
Mix Well: Blend dry ingredients thoroughly before adding buttermilk for even flavor and texture.
Handle Lightly: Keep the dough shaggy, not smooth. Minimal handling makes the bread tender.
Score the Top: Cut a deep “X” to help the bread bake evenly.
Check Early: Start checking a few minutes before the bake time ends, as ovens vary.