Preheat oven to 400°F. For baking you have a few options - baking sheet, pie dish, 2 loaf pans, or my favorite - a cast iron pan (the traditional choice!). If using a cast iron pan, stick it in the oven while the oven preheats.
In a large bowl, whisk together the flour, salt, baking soda, and sugar.
Cut your butter into small chunks and add it to the flour mixture. Using a pastry cutter or fork, break up the butter into the flour to leave behind pea sized pieces of butter through out the flour. Pour in the optional raisins and gently mix until it's spread throughout.
In a liquid measuring cup, measure out your buttermilk and whisk in the egg. Add this mixture to your bowl of flour. Gently fold it all together until it's mostly incorporated. Then transfer the dough to a lightly floured work surface and gently fold in the rest.
You want to be careful at this point not to overwork the dough. This isn't dough we knead. We just want to make sure all of the flour is evenly incorporated. Round out the dough into a ball and transfer to your cast iron pan (hot in the oven at this point), or other baking pan of choice.
Using a serrated knife, cut an 'X' in the center of the dough, allowing the center to bake evenly. If you're going for a sweeter approach, you can add a sprinkle of coarse sugar on top prior to putting it in the oven. (Not traditional, but delicious!) Place in the oven and bake for about 40 minutes, until bread is golden brown and center appears to be baked through. Remove from oven and let it cool for a few minutes before transferring to a cooling rack.
You can slice it into straight pieces like you see in the pictures or you can cut it up into triangles like a pie or pizza. I love serving this warm lathered with butter or jam. Makes a nice snack or served with a traditional hearty Irish meal such as a stew or meat and potatoes. Stays fresh in an airtight bag or container for a few days at room temperature (if it lasts that long!). Enjoy!