Preheat the oven to 425°F and line a baking sheet with parchment paper.

In a large bowl, whisk together the flour, baking powder, sugar, and salt.

On the large holes of a box grater, grate the frozen butter. Add to the flour mixture and toss to coat. Use your hands to work the butter into the flour until the mixture resembles a coarse meal.

Pour in the milk and mix with a wooden spoon until a shaggy dough forms. Knead with your hands to incorporate any remaining dry flour.

Turn the dough out onto a lightly floured surface and pat or roll into a 1/2-inch-thick rectangle. Fold the dough into thirds and pat or roll again until 1/2-inch thick. Rotate a quarter turn and repeat the folding and rolling process, then repeat two more times, rotating the dough a quarter turn each time. Dust your work surface with additional flour as needed if the dough starts to stick.

After the fourth time you fold the dough, pat or roll it into a 1/2-inch-thick rectangle again. Use a 3-inch biscuit cutter to cut out 6 biscuits, re-rolling the scraps as necessary. Place the biscuits on the baking sheet.

Bake for 14 to 16 minutes, or until the tops are golden brown. Let cool for 5 minutes before serving.