Preheat oven to 425°F and line a baking sheet with parchment paper.
Whisk together flour, baking powder, black pepper, salt, and 1 cup of grated white cheddar.
Using a pastry blender, cut in the chilled butter until it resembles coarse crumbs along with some slightly larger pea-sized pieces. Work as quickly as you can so the butter does not melt.
In a separate bowl, whisk together the sour cream and heavy cream.
Stir cream mixture into the dry ingredients, just enough until dough comes together.
Turn out dough onto a lightly floured surface and bring it together into a slightly flattened rectangle. Gently fold the dough in half over itself and pat it out again, then fold it over on itself again, making sure to bring in all the pieces. This will help create flakey layers.
Roll out dough to about an 8 inch by 5 inch rectangle and 1/2 – 3/4 inch thickness. Use a bench scraper or sharp knife to cut the dough into 15 equal squares.
Place scones on the baking sheet lined with parchment paper and brush the tops with cream. Sprinkle the tops with remaining cheese.
Bake for 12 – 14 minutes, until golden brown on the top and bottom.
Let cool before serving.