1. Preheat your oven to 400 F (200 C). Line a baking sheet with parchment paper or a silicone baking mat to prevent sticking and ensure even baking.

2. In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Make sure there are no lumps and everything is well distributed.

3. Add the cold, cubed butter to the dry ingredients. Using your fingertips, a pastry blender, or two knives, quickly cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces remaining. The colder the butter, the flakier your scones will be.

4. Pour in the sourdough discard, shredded cheddar cheese, and chopped chives or green onions. Use a spatula or your hands to gently mix until just combined. Be careful not to overmix, as this can lead to tough scones. The dough will be shaggy and a bit sticky.

5. Turn the dough out onto a lightly floured surface. Gently pat it into a round disc, about 3/4 to 1 inch thick. Using a sharp knife or a round biscuit cutter, cut the dough into 8 wedges or rounds. If using a cutter, gently re-form any scraps to cut additional scones, but handle them as little as possible.

6. Transfer the shaped scones to your prepared baking sheet, leaving a little space between each one. If desired, brush the tops with a little milk or buttermilk and sprinkle with a pinch of flaky sea salt for extra flavor and a golden crust.

7. Bake for 18-22 minutes, or until the scones are golden brown on top and a toothpick inserted into the center comes out clean. The internal temperature should reach around 200-210 F (93-99 C).

8. Remove the scones from the oven and let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely. They are best enjoyed warm.