1. Preheat your oven to 400 F (200 C). Line a baking sheet with parchment paper or lightly grease it.

2. In a large bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Make sure these are well combined to ensure even leavening throughout the biscuits.

3. Add the very cold, cubed 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. This is crucial for flaky biscuits.

4. In a separate medium bowl, combine the sourdough discard and buttermilk. Pour this wet mixture into the flour and butter mixture. Add the minced fresh chives, parsley, and rosemary. Gently mix with a spoon or your hands until just combined. Be careful not to overmix, as this can lead to tough biscuits. The dough will be shaggy.

5. 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 biscuits. For round biscuits, press straight down and lift; do not twist the cutter, as this seals the edges and prevents rising. For square biscuits, simply cut into squares. Gather any scraps, gently re-pat, and cut more biscuits.

6. Place the cut biscuits on the prepared baking sheet, leaving a little space between them. For softer sides, place them closer together; for crispier sides, space them further apart. Bake for 12-15 minutes, or until the tops are golden brown and the biscuits are cooked through.

7. If desired, immediately after removing them from the oven, brush the tops of the hot biscuits with a little melted butter for extra shine and flavor.

8. Allow the biscuits to cool slightly on the baking sheet before serving. They are best enjoyed warm.