Preheat the oven to 450° F and lightly grease a baking sheet or cast-iron skillet.
Mix together the flour, baking powder, sugar, and salt.
Cut the stick of butter into pieces, and work into the flour mixture with your hands or a pastry blender until it resembles pea-sized crumbs.
Add the liquid, stirring until a bit loose and sticky.
Pour the dough out on a floured surface, and knead for a minute. Dough should be smooth and no longer wet. You can sprinkle more flour on the surface if you find it’s sticking.
Take the dough into a ball, and hit it with a rolling pin, turning it and folding it in half every few whacks. Do this for a couple of minutes.
Roll out dough until it’s 1/4” thick, and then fold it in half. Using a round cutter (can use a glass or a cup if don’t have a biscuit cutter) cut out your biscuits from the folded dough.
Place on a greased baking sheet close together (so they rise up not out), and bake for 15 minutes or until the tops are golden brown.
If you don’t want to roll and cut them out, after kneading and beating the dough you can drop the dough onto the baking sheet with a spoon. They’re not as symmetrical (dropped biscuits are also known as cat head biscuits) but they’re no less delicious.