Combine all the dry ingredients (flour, sugar, salt, baking powder) in a large bowl.
Add the butter to the flour mixture. Using your hands, pinch the butter pieces and mix it into the flour until a flaky mixture results. Alternatively, use a pastry cutter.
In small bowl, whisk together the egg and yogurt.
Make a well within the flour mixture and in small batches, add the yogurt mixture, making sure that the batter is thoroughly mixed before adding more yogurt mixture. It will get sticky, but be patient to let everything combine well.
Once the scone dough holds together completely, add the cranberries and white chocolate chips, lightly kneading them into the dough.
Reshape the dough into a rough circle, fairly thick, about 1.5-2 inches high. Let it rest in the fridge for 30 min.
Preheat the oven to 350ºF.
Using a sharp knife, cut the scone dough into 8 pie slices and place onto a baking sheet. If desired, sprinkle sugar on top of the scones for a crispier outer layer.
Bake for about 18 minutes, or until barely golden.