Preheat your oven to 400 degrees F (200 degrees C). While the oven heats up, cube the butter into small pieces and place them in the freezer. This will help keep the butter cold, which is essential for creating that flaky texture.
You can make soda bread in virtually any oven-proof pan that’s large enough. A seasoned cast iron skillet works wonderfully, or you can line a baking sheet with parchment paper for easy clean-up.
In a large bowl, whisk together the flour, sugar, baking soda, and salt. Ensure everything is evenly combined; this helps the bread to rise uniformly.
In a liquid measuring cup, whisk the buttermilk and optional egg together. Refrigerate this mixture until you’re ready to use it.
Using a pastry cutter or your fingers, cut the cold butter into the flour mixture until it resembles pea-sized crumbs. If you’re adding raisins, stir them in now. Work quickly to keep the butter chilled, as this helps the dough remain less sticky.
Create a well in the center of your dry ingredients, then pour in the chilled buttermilk and egg mixture. Using a stiff spatula or wooden spoon, fold the mixture together until it becomes too difficult to stir.
On a lightly floured surface, transfer the dough and shape it into a shaggy ball. Don’t worry if it’s sticky; this is normal. Just sprinkle it lightly with flour to make it manageable. Avoid adding too much flour or over-kneading, as this will result in a tough loaf.
Transfer the dough to your prepared pan. If desired, sprinkle with coarse sugar. Using a knife, score the top with a deep “X” to allow for even baking and to give the bread character.
Bake in the center of your preheated oven for 45 to 55 minutes. You’ll know it’s ready when the internal temperature reaches 190 degrees F (88 degrees C) on an instant-read thermometer. This ensures the bread is thoroughly baked.
Once baked, carefully transfer the bread to a wire rack using oven mitts. Allow it to cool for at least 15 minutes before slicing. The rustic texture of the bread makes for delightful, albeit imperfect, slices!