Whisk together the flour, baking powder, baking soda, and brown sugar in a large bowl.
Cube the cold butter. Try not to touch it with your fingers as that will warm it up.
Pour the dry ingredients and the cubed butter into your prepared food processor.
Pulse about ten times. Your butter will look like dots. NOTE: Never put your fingers into a food processor to check on the ingredients.
Add the buttermilk and egg to the butter and flour mixture.
Pulse until the wet and dry ingredients are just mixed. Do not over mix.
Dust a work surface, and your hands, with flour.
Pour the dough out onto the lightly floured surface. It is very sticky!
Add the raisins to the top of the dough.
Knead the dough about ten times until the raisins are incorporated.
Line a baking sheet with parchment paper.
Form the dough into a round loaf and carefully transfer it to the prepared baking sheet.
To form the scones, cut through vertically and horizontally the top of the loaf with a sharp knife. You can also use a bench scraper or a pizza wheel.
Cut each quarter loaf in half to make eight scones.
Spread out the scones on the parchment paper.
Place the baking sheet into the fridge for about 30 minutes.
Near the end of the chilling time, preheat the oven to 350 degrees.
Remove the chilled scones from the fridge and brush the top and sides of each one with a bit of heavy cream.
Sprinkle a bit of sparkling sugar on top of each scone. This step is totally optional!
Bake for 24-28 minutes until golden brown.
Let cool on the baking sheet for 5-10 minutes, then transfer to a wire rack.