In a large bowl, whisk together the flour, brown sugar, salt, and baking soda.
Using your fingers (or a pastry cutter), work the butter into the flour mixture until well combined. I definitely prefer to use my hands for this. The mixture will resemble crumbly sand. Stir in the raisins.
Mix in the beaten egg and buttermilk with a wooden spoon until combined.
Use a bit of flour on the countertop and gently knead the dough just long enough to form a rough ball. Be really careful not to over knead. If you over knead, the bread will come out tough. This bread will be a bit sticky, if it is too sticky to work with, add a bit more flour. But you also want to be careful not to add too much.
Place the dough ball into a lightly greased cast iron skillet. I use a 10 inch skillet and I also use parchment paper for easy clean up!
Use a knife to score the top of the dough into an "X" about an inch deep.
Bake about 40-45 minutes or until a wooden skewer inserted comes out clean.
Allow to rest about 5-10 minutes and then remove the bread from the skillet.