Preheat your oven to 400°F (200°C).

Line a baking sheet with parchment paper or a silicone baking mat.

In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt.

Add the cold butter cubes to the flour mixture and cut in using a pastry cutter or fork until it resembles coarse crumbs.

In another bowl, mix the sourdough discard, milk, and vanilla extract.

Pour the wet mixture into the dry ingredients and stir gently until just combined.

If using add-ins, fold them into the dough.

Turn the dough onto a floured surface, pat into a circle about 1-inch thick, and cut into wedges.

Place the wedges on the prepared baking sheet and bake for 15 minutes or until golden brown.