Preheat the oven.
Heat your oven to 425°F. Line a baking sheet with parchment paper.
Mix the dry ingredients.
Whisk together the flour, baking powder, sugar, and salt.
Add the cold butter.
Cut the butter into small cubes and work it into the flour using your fingertips or a pastry cutter. Stop when you still have lots of pea-sized pieces of butter.
Those pieces are important—they melt in the oven and create steam, helping make the biscuits flaky and fluffy.
Add the milk.
Pour in 1¼ cups cold milk and gently stir until a shaggy dough forms. Don't overmix. If the dough is still very dry, add milk 1 tablespoon at a time.
Fold for flaky layers.
Turn the dough onto a lightly floured surface. Gently press it into a rectangle.
Fold it into thirds like a letter. Turn it 90°, flatten it gently, and fold it into thirds again.
Make them nice and thick.
Pat the dough to about 1–1¼ inches thick. Cut out the biscuits with a 2½- to 3-inch biscuit cutter.
Push the cutter straight down without twisting.
Bake.
Place the biscuits on the baking sheet with their sides just touching. Bake for 14–17 minutes, or until tall and golden on top.
Finish with butter.
Brush the hot biscuits generously with melted butter.