Preheat oven to 350°F. In a large bowl, whisk together the flour, sugar, baking powder, and salt. Add the cold, cubed butter to the flour mixture. Use a pastry blender or two knives to cut the butter into the flour mixture until crumbly. Add the raisins to the flour mixture and set aside. In a separate bowl, whisk together the egg and 1/2 cup of heavy cream. Combine the wet and dry ingredients, mixing until just combined. Work the dough into a disk approximately 1 1/2 inches thick and 6 inches in diameter. Cut the disk into 8 small triangles. Place the scones on a parchment-lined baking sheet. Brush the tops of the scones with additional heavy cream and sprinkle with a little sugar. Bake for 20 minutes, or until golden brown.
