Step 1

Position a rack in the middle of the oven and preheat the oven to 375°F. Line a baking sheet with parchment. In a large mixing bowl, whisk together both flours, the fine sea salt, baking powder, sugar, and baking soda. Add the cold butter cubes and toss to coat. Working quickly, cut in the butter with a pastry blender, or pinch the cubes with your fingertips, smearing them into the flour. You should have various-sized pieces of butter ranging from coarse sandy patches to flat shaggy shards to pea-sized chunks. Give the ingredients a good toss with your hands to make sure all the pieces of butter are completely coated in flour.

Step 2

Make a well in the center of the dry ingredients, pour in the buttermilk, and use your hands to mix the dry ingredients into the buttermilk until you have a shaggy dough. Gently turn the dough out onto a clean work surface. The dough should still look crumbly. Now be prepared to get messy! Using the heel of your hand, smear the butter into the flour—that is how you build those flaky layers. Bring the dough together by smearing, folding, and turning it, then repeat until there are no more dry bits of flour remaining and the dough comes together in a mass.

Step 3

Flour a rolling pin and lightly dust your work surface with flour. Roll the dough into a 12-by-14-inch rectangle, with a long side toward you. Begin by doing a tri-fold, starting from the right: Fold the right side of the dough over the center and then fold the left side over the first fold, lining up the edges and pressing the layers together. Rotate the dough 90 degrees and roll it out again into a rectangle, then fold the dough in half from the top down, pressing the layers together. Roll the dough out again into a rectangle and fold it in half once more, pressing the layers down again. Then, using a bench scraper or a sharp knife, cut the dough in half and stack the bottom half on the top half, pressing the layers together. Dust the dough lightly with flour, and roll the dough out again into a rectangle about 1 inch thick.

Step 4

Dip the edges of a 2¼-inch biscuit cutter in flour and punch out the biscuits; do not twist the cutter, or you will seal the layers of the dough you have worked so hard to create, and the biscuits will not rise as high. Make sure to dip the cutter in flour after every cut, and arrange the biscuits 1 inch apart on the prepared baking sheet. Then carefully gather up your scraps, press them together until you have a cohesive mass, roll them out again, and cut more biscuits. The scrap biscuits may bake a little topsy-turvy, but that’s okay; they will still be flaky and delicious. (If you don’t want to bake all the biscuits at once, you can freeze some on a baking sheet until solid, then wrap and freeze them to bake at a later date. You can bake them directly from the freezer; just give them 5 to 7 extra minutes in the oven.) You can bake the biscuits now or refrigerate them for up to 1 hour before baking.

Step 5

Brush the tops of the biscuits with the melted butter and give each one a sprinkle of flaky sea salt. Bake, rotating the pan halfway through for even baking, for 25 to 30 minutes, until golden brown. The biscuits are best served hot out of the oven (you will want to taste one immediately, and give yourself a pat on the back).

Step 6

If you have any leftovers, store them in an airtight container for up to 1 day. To reheat, place the biscuits on a wire rack in a preheated 350°F oven for 5 to 6 minutes. To freeze leftover biscuits, wrap in foil and place in a large ziplock bag. To reheat the biscuits, place the foil-wrapped biscuits in a 350°F oven for 18 to 20 minutes, then carefully open the foil and bake for an additional 5 minutes.