PREHEAT oven to 450F. Line a baking sheet with parchment. Whisk flour, baking powder, sugar, salt, garlic powder and baking soda in a large bowl. Grate butter into flour mixture
and toss to coat. Add cheddar and green onions and gently stir until coated.
RESERVING 2 tbsp, stir buttermilk into flour mixture until dough just comes together. Do not over-mix. Turn out onto lightly floured surface, lightly knead 3 times and pat out until 1-in. thick.
CUT out 12 rounds using a 2 ½-in. round cutter, gathering and rerolling extra dough, or cut into 12 squares using a sharp chef’s knife, and arrange 1 in. apart on prepared sheet. Brush with reserved buttermilk.
BAKE until tops are golden brown, about 14 min. Transfer to a rack and brush with melted butter Tip: Cold, grated butter is key to a perfect biscuit. When the hot oven hits the cold butter bits, it creates steam, which pushes everything up for a high-rising, flaky biscuit.