1-Step 1: Prepare Your Wet Ingredients Start by whisking together your sourdough discard and egg in a medium bowl until fully combined. The mixture should be relatively smooth with no streaks of egg remaining. If your discard has been sitting in the fridge for a while and has developed a layer of liquid (called hooch) on top, simply pour that off before measuring. Give the discard a good stir to recombine any separated portions before adding the egg.

2-Step 2: Mix the Dry Ingredients In a separate large bowl, stir together the all-purpose flour, baking powder, and fine sea salt until evenly distributed. This ensures the leavening and salt are spread throughout the flour so every biscuit has consistent flavor and rise.

3-Step 3: Grate and Incorporate the Frozen Butter This is where the magic happens. Using the large holes of a box grater, grate your frozen butter directly into the flour mixture. Work quickly and be sure to scrape any butter stuck to the inside of the grater into the bowl. Toss the grated butter with the flour mixture, rubbing gently between your fingers so the flour coats the butter strands. You want to see distinct pieces of butter throughout the flour. If you’re adding cheese, now is the time to toss it in with the butter-flour mixture.

4-Step 4: Combine Wet and Dry Ingredients Make a well in the center of your flour-butter mixture and pour in the discard-egg mixture. Using a spatula, stir gently until the dough is mostly combined with just a few dry bits remaining. The dough will look shaggy and somewhat rough, which is exactly what you want. Overmixing at this stage develops gluten and leads to tough biscuits.

5-Step 5: Gentle Kneading and Folding Turn the dough out onto your counter and knead gently for about 10 seconds, just enough to bring everything together into a cohesive mass. Don’t overwork it, as the heat from your hands can melt the butter. Roll the dough with a rolling pin until it’s about 1/2 inch thick. Now comes the layering technique that makes these biscuits so flaky: 1. Fold one third of the dough over toward the middle, like folding a business letter. 2. Fold the opposite third over the first fold. 3. Fold the short edges in to form a square shape. 4. Roll the square out to 3/4 inch thickness. This folding creates the layers that will puff and separate during baking.

6-Step 6: Cut the Biscuits Dip your biscuit cutter in flour, then press straight down through the dough and lift straight out. Do not twist the cutter. Twisting seals the edges and prevents the biscuits from rising properly. Place cut biscuits on a parchment-lined baking sheet. Gently press the scraps together and cut additional biscuits until all dough is used.

7-Step 7: Freeze Before Baking Place the baking sheet with the cut biscuits in the freezer for about 10 minutes while you preheat the oven to 450°F. This step is crucial for maintaining the cold butter temperature, which creates steam pockets and maximum rise.

8-Step 8: Bake to Golden Perfection If desired, sprinkle a little extra cheese on top of each biscuit. Bake on the middle rack for 18 to 22 minutes, or until the tops are deeply golden brown. Transfer to a wire rack to cool slightly before serving warm.