Grate the cold butter using a box grater. Spread the grated butter it in a single layer on a plate or baking sheet. Freeze for 15 minutes, or until solid.
In a large bowl, whisk together the flour, baking powder, baking soda, sugar, and salt.
Add the frozen, grated butter to the flour mixture. Use your fingertips to gently toss and pinch the butter into the flour until it’s evenly distributed and resembles coarse crumbs. Be careful not to overwork the butter to prevent it from melting or becoming too warm.
Pour in the buttermilk and stir until the dough comes together. Use your hands to bring it together if necessary, just be careful not to overmix.
Turn the dough onto a floured surface and roll it into a long rectangle, about 1 inch thick.
Cut the dough into thirds and stack the pieces on top of one another—alternatively, fold the dough into thirds. Rotate the dough 90° or a half-turn.
Repeat two more times: Roll out the dough, cut and stack or fold the dough into thirds, and rotate.
For the final roll, roll the dough to about 1 inch thick.
Use a biscuit cutter or sharp knife to cut the dough into rounds or squares, about 2 inches wide. Place the biscuits on a parchment-lined baking sheet.
Chill the biscuits in the refrigerator for about 15 minutes. Meanwhile, preheat the oven to 425°F.
Brush the tops of the biscuits with buttermilk. Bake for 12-14 minutes, or until golden brown.
Notes
When using a round biscuit cutter, you may wish to re-roll any scraps to use up all of the biscuit dough.
Recipe yields about 8 (2-inch) biscuits but may vary depending on the size you make the biscuits.
Note that ovens vary, so use your best judgement for baking times, you may need a few more/less minutes to achieve the golden brown color.
For the best results, use the recommended gluten-free flour (Cup4Cup or my copycat version). Refer to the blog post for more tips and substitutions. The recipe is pretty fool-proof but I have provided weighted measurements for accuracy; click the "metric/grams" button at the top of the ingredients list to access those measurements.