Preheat oven to 425º
Combine the flour, baking powder, and salt in a medium bowl. Whisk to evenly disperse.
Add the diced butter to the bowl and toss to coat in the flour. With your fingers, pinch the butter into the flour until all of the cubes have turned into thin ribbons of butter. Toss the mixture again to lighten, then form a well in the center.
Pour in the sourdough discard and stir the mixture with a spatula until a shaggy dough forms. When it becomes too thick to stir, start to knead the dough by hand. Be sure to incorporate any flour remaining at the bottom of the bowl and stop as soon as the dry bits are all mixed in.
Turn the dough out onto a lightly floured surface and roll out to a 1 inch thick square.
Divide the dough into four equal size pieces. Stack the pieces together and roll out into to 1 inch thick rectangle that is 5 x 12 inches wide.
Cut out rounds using a 2 1/2 inch biscuit cutter, reforming the scraps until all of the dough has been used. Transfer the rounds to a parchment lined baking sheet and chill for at least 30 minutes before baking.
Pull from the refrigerator and immediately place into the center of a preheated oven. Bake for 20 minutes, or until perfectly golden on top.