Preheat oven to 450°F (232°C)
Line a baking sheet with parchment paper
Whisk together 2 cups all-purpose flour, 1 tablespoon baking powder, 1 tablespoon sugar, and 1/2 teaspoon salt
Cut in 1/2 to 3/4 cup cold unsalted butter until the mixture resembles coarse crumbs
Stir in 3/4 to 1 cup cold milk (or buttermilk) just until dough comes together
Turn dough onto a lightly floured surface and gently pat to about 1-inch thickness
Fold dough over itself 1 to 2 times, then pat to 1-inch thickness again
Cut biscuits with a round cutter, placing them close together on the baking sheet
Gather scraps, pat again, and cut more biscuits (avoid overworking)
Brush tops with melted butter (optional)
Bake 10 to 14 minutes, until risen and golden brown
Cool 2 to 5 minutes before serving