These are wonderful and very versatile. Feel free to substitute your favorite cheese in place of the parmesan and whatever extra for the scallions. I have made these biscuits with scallions, chives, green and black olives, and sun-dried tomatoes. They are great with blue cheese and cheddar cheese, as well.
Preheat the oven to 425F. In a large bowl whisk together the flour, cayenne, black pepper, baking powder, sugar, and salt. Set aside.
Dice the butter and toss with the flour mixture until finely coated. Add the scallions and parmesan cheese and toss until finely coated. Add the buttermilk and mix with your hands until it just comes together. (You will get messy. Just accept it.) Do not over-knead.
Form into an 8x8 square on a lightly floured service. Cut into squares and top with a bit of nice sea salt. Bake for 12-16 minutes or until golden.