To a medium bowl, add the flour, sugar, salt, and baking powder. Grate chilled butter and add to the dry mixture. In a separate small bowl, beat the egg and buttermilk together and pour into the dry mixture. Stir batter until it starts to come together. Fold in the cranberries and white chocolate and turn out onto a well-floured surface.
Gently press down the dough into a 10-inch round. Cut the round into 8 wedges and place on a baking sheet lined with a silicone baking mat or parchment paper about 1 1/2″ apart. Sprinkle with coarse sugar. Place in the oven and bake for 18-20 minutes.