These flaky sourdough buttermilk biscuits are my take on a southern classic. They're light and crumbly but still hold their shape enough to sandwich some eggs and bacon in the middle.
In a large bowl, whisk together the flours, baking powder, baking soda, salt, and sugar.
Cut the cold butter into the dry ingredients by flattening the cubes into disks. You want the butter to remain in relatively large chunks (about quarter sized).
Pop the entire bowl into the freezer for about 5 minutes to let the butter firm back up.
Remove the bowl from the freezer and gradually stir in the sourdough discard until it's incorporated throughout the flour.
Slowly drizzle buttermilk over top, combining as you go. Knead a few times in the bowl until you have a very dry, shaggy dough.
Turn the dough out onto a clean surface and shape the dough into a 1 inch thick square.
Using a knife or bench scraper, cut dough into 4 equal pieces. Stack pieces on top of one another, sandwiching any loose dry bits of dough between layers, and press down to flatten.
Roll dough into a 1 inch thick rectangle (about 9x9) and cut into 9 square biscuits (you can instead use a round biscuit cutter).
Transfer the biscuits to a parchment lined baking sheet and pop in the freezer for 10 minutes before baking.
While the biscuits are chilling, preheat the oven to 400°F.
Remove the biscuits from the freezer and brush tops with melted butter and sprinkle with flaky sea salt.
Bake biscuits for 20 to 25 minutes or until golden brown on top.
If you don't have cake flour, you can use all-purpose flour instead but your biscuits will be a little less light and tender.If you don't have buttermilk, substitute ¾ cup whole milk + 2 teaspoons lemon juice.