In a large bowl or a food processor, combine flour, baking powder, baking soda, and salt.

Cut in the butter with either a pastry cutter, fork, or food processor.

Stir in the sourdough discard and milk until a shaggy dough forms. Add a splash more milk if dry.

Turn out dough onto a lighly floured surface. Pat into a 1 inch thick rectangles. Fold and pat 2-3 times to build layers.

Cut biscuits with a floured circle cutter (a cup works great!)

Bake at 425 F for 12-15 minutes until golden brown. Optional to brush with butter after baking.