Preheat oven to 450 degrees.
Sift (or whisk) the flour, baking powder, salt, and sugar in a medium bowl. With a pastry blender or fork, cut the butter into the flour mixture until the mixture resembles coarse crumbs. Pour in the milk all at once. Stir quickly with a fork just until the dough clings together; do not overmix.
Turn the dough onto a lightly floured surface and knead gently 10-12 times. Excess handling makes biscuits tough. Just be sure all the ingredients are well-distributed throughout the dough. Gently roll or pat the dough to about 1/2 inch thick. Press a floured 2-inch biscuit cutter into the dough and swivel once or twice to make sure it has cut through. Dip the cutter into flour between cuts. Gather up the dough scraps into a ball and pat out again to cut one or two more biscuits.
Place the biscuits close together in a square baking pan and bake until light brown, about 12 minutes. Serve warm, right out of the oven.