Line a baking sheet with parchment paper.
In a large bowl, whisk together the flour, baking powder, sugar, garlic powder, salt and pepper.
Grate the butter on the large hole of a box grater. (Alternately, dice it into small cubes.)
Add the butter to the bowl with the flour, and using your fingers, work the butter into the flour until the texture resembles small pebbles.
Add the buttermilk, shredded cheddar cheese and chives, and using a spatula, mix together the ingredients just until combined.
Lightly flour your work surface then turn out the dough. Using your hands, gather and knead the dough just until it is cohesive. (Do not overknead the dough.)
Using a rolling pin, roll out the dough until it’s 1/2-inch thick. Fold it into thirds (like a letter) then rotate the dough 90° and roll it out again until it is a 10x6-inch rectangle that’s 3/4-inch thick.
Using a sharp knife, cut the rectangle into 9 rectangular biscuits. Arrange the biscuits on the prepared baking sheet then brush the tops of them with buttermilk. Place the baking sheet in the freezer for 15 minutes.
Preheat the oven to 425°F.
Bake the biscuits until they are golden brown and no longer doughy, 15 to 18 minutes. Remove the biscuits from the oven and serve.