1. 1. Prepare Your Dry Ingredients: In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Make sure there are no lumps and the ingredients are evenly distributed. This ensures a consistent rise and flavor throughout your biscuits.

2. 2. Cut in the Cold Butter: Add the very cold, cubed unsalted butter to the dry ingredients. Using a pastry blender, two knives, or your fingertips, cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining. The colder the butter, the flakier your biscuits will be, so work quickly to prevent it from melting.

3. 3. Incorporate the Cheese and Sourdough Discard: Stir in the shredded sharp cheddar cheese until it’s evenly distributed throughout the butter and flour mixture. Then, add the sourdough discard and gently mix until just combined. The mixture will still be crumbly at this point.

4. 4. Add the Buttermilk: Pour in the buttermilk and mix with a spoon or your hands until a shaggy dough forms. Be careful not to overmix; overmixing can lead to tough biscuits. The dough should still look a bit rustic and not perfectly smooth.

5. 5. Form the Biscuits: Turn the dough out onto a lightly floured surface. Gently pat the dough into a rectangle about 3/4 to 1 inch thick. Use a 2-inch biscuit cutter or a sharp knife to cut out your biscuits. For round biscuits, press straight down and lift; do not twist the cutter, as this can seal the edges and prevent a good rise. For square biscuits, simply cut the rectangle into squares. Gather any scraps, gently re-pat, and cut out more biscuits.

6. 6. Arrange and Bake: Place the cut biscuits on a parchment-lined baking sheet, leaving about 1 inch between them for even cooking. If desired, brush the tops with a little extra buttermilk for a golden finish. Bake in a preheated oven at 425 F (220 C) for 15-20 minutes, or until the tops are golden brown and the biscuits are cooked through.

7. 7. Cool Slightly and Serve: Once baked, remove the biscuits from the oven and let them cool on the baking sheet for a few minutes before transferring them to a wire rack. They are best served warm, straight from the oven, when they are at their fluffiest and cheesiest.