Preheat oven to 375°F (190°C). Line a large baking sheet with parchment paper or a silicone baking mat and set aside.
In a large mixing bowl, whisk together the flour, sugar, baking soda, and salt until well combined. Add the cold cubed butter and cut it into the dry ingredients with a pastry cutter or fork until you have small pea-sized crumbs. Stir in the raisins and set aside.
In a separate mixing bowl, whisk together the buttermilk and egg until fully combined. Pour the mixture into the dry ingredients and gently stir the dough together until just combined. The dough will be a little sticky, this is okay.
Turn the dough out on a floured surface, flour the top of the dough and your hands, then knead the dough together a few times adding more flour as needed until you can form it into a ball that's about 7-inches in diameter.
Cut an 'X' into the top of the bread and brush with a little extra buttermilk if desired.
Bake at 375°F (190°C) for 45-60 minutes or until the top of the bread is browned and a toothpick inserted into the center of the bread comes out clean. Remove from the oven and allow the bread to cool for 15-20 minutes before slicing into it.