01 - Preheat oven to 400°F and line a baking sheet with parchment paper.
02 - Whisk together flour, baking powder, salt, and black pepper in a large bowl.
03 - Add cold cubed butter; rub into flour mixture with fingertips or pastry cutter until coarse crumbs form.
04 - Stir in grated cheddar cheese and chopped chives until evenly distributed.
05 - Whisk whole milk and sour cream together in a separate bowl.
06 - Pour wet ingredients into dry mixture and gently stir with a fork until just combined; avoid overmixing.
07 - Turn dough onto a lightly floured surface and pat into a 1-inch thick round.
08 - Cut dough into 8 wedges and place on prepared baking sheet.
09 - Brush wedge tops with milk and sprinkle with extra grated cheddar if desired.
10 - Bake for 16 to 18 minutes until golden brown. Allow to cool slightly before serving.