1-First Step: Mise en place and mixing wet ingredients Gather all ingredients and tools: a box grater, mixing bowls, a spatula, a biscuit cutter, parchment paper, a rolling pin, a baking sheet, and an oven thermometer if you have one. Measure ingredients on a kitchen scale for best accuracy. Whisk together the 195 grams sourdough starter discard and 1 large egg in a medium bowl. Set aside in the refrigerator briefly if your kitchen is warm; cold discard helps keep the butter solid during mixing.

2-Second Step: Combine dry ingredients In a separate bowl, combine 170 grams all-purpose flour, 2 teaspoons baking powder, and 3/4 teaspoon fine sea salt. Mix with a fork or whisk so the leavening is evenly distributed.

3-Third Step: Add frozen butter for flaky layers Using the large hole side of a grater, grate 115 grams (8 tablespoons) of frozen unsalted butter directly into the flour mixture. Scrape any remaining butter from the grater into the bowl. Toss the grated butter with the flour, then gently rub the butter into the flour just enough to coat the pieces. The goal is to keep butter pieces intact so they steam while baking, creating layers. If using 2 ounces shredded cheese, add it now and toss to combine with the flour and butter.

4-Fourth Step: Combine wet and dry Create a well in the center of the flour mixture and pour in the sourdough-egg mixture. Stir with a spatula until only a few dry spots remain; the dough will be shaggy and slightly sticky. Avoid overmixing because that warms the butter and develops gluten too much.

5-Fifth Step: Light kneading and folding for layers Transfer the shaggy dough to a lightly floured counter. Knead lightly for about 10 seconds just to bring it together. Roll the dough to about 1/2-inch thickness. Perform an envelope fold: fold one-third over the middle, then fold the other third on top. Turn the dough so the short edges are folded toward the center to form a rough square. Roll the square to 3/4-inch thickness. These folds create visible layers once baked.

6-Sixth Step: Cutting biscuits correctly Flour a biscuit cutter and press straight down and pull straight up without twisting. Twisting seals the edges and prevents vertical rise. Gently gather scraps, press lightly, and cut additional biscuits until dough is used. Place biscuits on a parchment-lined baking sheet spaced slightly apart.

7-Seventh Step: Chill then bake Place the tray of cut biscuits in the freezer while you preheat the oven to 450°F. Freezing for even a few minutes helps keep the butter cold and produces flakier layers. If you like, sprinkle a little extra cheese on top now. Bake on the middle rack for 18-22 minutes, until the tops are golden brown. Use an oven thermometer for accuracy if needed. Remove from oven and cool briefly on a wire rack before serving.

8-Final Step: Serving and timing Serve warm. These biscuits are best the day they are baked but are still good reheated.