In a medium bowl, whisk together flour, baking powder, baking soda, sugar, and salt.
Grate the frozen butter into the flour mixture.
Add the frozen cranberries and white chocolate to the flour mixture, and toss to combine.
Pour the cream into the flour and gently mix using your hands, until combined. The dough will be slightly dry and perhaps a touch crumbly, but this will result in a flaky pastry.
Turn the dough out onto a lightly floured surface. Form the dough into a disk, about 1 inch thick. At this point you can cut the scones into your desired shape. You can use a biscuit cutter and make rounds, or cut them into wedges.
Transfer the scones to a parchment lined baking sheet, and brush lightly with cream, and sprinkle with coarse sugar.
Bake for 20-25 minutes, until the scones are golden brown.