Preheat the oven: Set it to 450°F (232°C). Line a baking sheet with parchment or lightly butter a cast-iron skillet.

Mix dry ingredients: In a large bowl, whisk 2 cups all-purpose flour, 1 tablespoon baking powder, 1/2 teaspoon baking soda, and 3/4 teaspoon salt.

Cut in the butter: Grate 1/2 cup (1 stick) very cold butter on the large holes of a box grater, or cube it. Toss into the flour and cut in with a pastry cutter or your fingers until pea-sized bits remain.

Combine wet ingredients: In a small bowl, stir 1 cup sourdough discard with 1/2 cup cold buttermilk (start with 1/3 cup if your discard is runny). You want a thick, scoopable mixture.

Bring the dough together: Pour the wet mixture into the flour. Gently fold with a spatula until shaggy and just combined. If it’s too dry, add a tablespoon of buttermilk. If too sticky, sprinkle in a tablespoon of flour.

Pat and fold: Turn the dough onto a lightly floured surface. Pat into a rectangle about 3/4-inch thick. Fold it in thirds like a letter. Turn, pat again, and repeat 2 more times. This creates layers.

Shape and cut: Pat to 1-inch thickness. Use a round cutter (2 to 2.5 inches) to cut straight down—don’t twist. Gently press scraps together and cut more. You’ll get 8–10 biscuits.

Pan placement: For taller biscuits, place them so their sides touch. For crisper edges, space them an inch apart on the sheet.

Top and bake: Brush tops with a little milk or melted butter if you like. Bake 12–15 minutes until risen and deep golden on top.

Finish: Brush with more melted butter while warm. Let them rest 5 minutes before splitting.