Preheat the oven to 425°F . Line a large baking sheet with parchment paper and set aside.
Lightly flour your work surface.
In a large mixing bowl, whisk together the flour, baking powder, sugar, and salt until well combined.
Grate the frozen butter into the mixture, and toss with a fork to work the butter throughout.
Pour the buttermilk into the mixture and gently mix until the dough starts to come together.
Turn out the dough onto your prepared work surface.
Pat the dough into a rectangle using your hands.
Take one end of the rectangle and fold it over to the other. Gently flatten back into a rectangle. Repeat this twice more, then flatten into a rectangle again that is about 1/2 inch thick.
Use a biscuit cutter and cut as many biscuits as you can.
Gently bring together the scraps, then cut out more biscuits. You should get 8 biscuits total.
Place the biscuits on the prepared baking sheet.
Brush the top of each biscuit with buttermilk.
Bake for 14-15 minutes or until lightly golden brown all over.
Remove the pan from the oven and immediately brush the tops of the biscuits with the melted salted butter.