Preheat the oven to 425˚ F.
Combine the flour, baking powder, sugar and salt in a food processor. Pulse to combine.
Pulse in the diced butter just a few times, until it is in pea-size pieces.
Transfer the mixture to a large bowl. Stir in the milk or buttermilk until the dough just comes together but is not fully combined.
Turn out onto a lightly floured surface, then gather the dough together and pat into a ¾-inch-thick rectangle (5 by 10 inches).
Fold the rectangle in half and pat until ¾ inch thick again. Repeat the folding and patting process 4 more times, ending with a ¾-inch-thick rectangle (5 by 10 inches).
Dip a 2 ½-inch round biscuit cutter in flour and cut out 8 biscuits, going all the way to the edge of the rectangle (don’t leave any space between the biscuits when you cut).
Gather the scraps together, kneading as little as possible; pat until ¾ inch thick and cut out about 2 more biscuits.
Place the biscuits on an ungreased, unlined baking sheet. Brush the tops lightly with milk or buttermilk.
Bake until golden, 12 to 15 minutes.
