In a large bowl, add the flour, baking powder, baking soda, sugar and salt. Whisk until thoroughly combined.

Grate frozen butter with a box grater and mix with the dry ingredients until the butter is coated with the flour mixture and crumbly, pea-sized pieces.

In a liquid measuring cup, whisk together the cold sourdough discard and cold buttermilk until smooth. Create a well in the center of the flour mixture and pour the wet ingredients into the dry ingredients. Mix with a fork or a rubber spatula until a shaggy dough is formed.

Pour the dough onto a floured surface and gently pat the dough until the flour mixture just comes together into one mass and shape the dough into a large rectangle.

Using a floured rolling pin, roll out the dough into a large rectangle, fold it in half the long way, and then fold it in half again. Roll out the dough into a large rectangle again and fold the exact same way once more.

For a third time, pat the biscuit dough with your hand until it is ½ inch tall. Take a 2 ¾ inch sharp biscuit cutter and dip it into flour, then cut into the dough.

Re-roll the scrapes and repeat until 8-9 sourdough biscuits have been formed.

Preheat the oven to 425 degrees F.

Place the Sourdough Biscuits ½ inch apart on a baking sheet lined with a piece of parchment paper.

Cover the biscuit dough and place them into the freezer for at least 20 minutes, while the oven preheats.

After the biscuits have chilled and the oven is preheated, bake the Sourdough Biscuits for 17-20 minutes.

While the biscuits are still hot, use a pastry brush to brush the tops of the biscuits with melted butter and sprinkle flaky sea salt on top.