Preheat your oven to 425°F (220°C). A hot oven is essential for getting a good, quick rise from the biscuits. Line a large baking sheet with parchment paper to prevent sticking and make cleanup easy.
In a large mixing bowl, add the all-purpose flour, baking powder, kosher salt, and sugar. Use a whisk to stir them together for about 30 seconds. This step is more effective than using a spoon as it ensures the baking powder and salt are evenly distributed, so every biscuit rises perfectly.
Take your butter directly from the refrigerator. Using the large holes of a box grater, grate the cold butter right into the flour mixture. Gently toss the butter with the flour using a fork or your fingertips until the mixture looks like coarse crumbs with some pea-sized pieces of butter still visible. Work quickly to prevent the butter from melting. The less you handle the dough, the more tender your biscuits will be.
Create a well in the center of your flour-butter mixture and pour in most of the milk. Using a fork or a rubber spatula, gently stir until a shaggy, slightly sticky dough forms. Do not overmix! It’s okay if there are a few dry spots. If the dough seems too dry, add the remaining milk, one teaspoon at a time, until it just comes together. The dough should be moist, not wet.
Using a large spoon or a 2-tablespoon cookie scoop, drop mounds of dough onto the prepared baking sheet. Space them about 2 inches apart to give them room to spread as they bake. For an extra golden-brown top, you can lightly brush the tops with a little milk before baking.
Place the baking sheet in the fully preheated oven and bake for 12-14 minutes. The biscuits are done when their tops are a beautiful light golden brown and a toothpick inserted into the center comes out clean.
As soon as you remove the biscuits from the oven, brush the tops with a little melted butter. This adds extra richness and a soft, appealing shine. Serve warm.