In a large mixing bowl, whisk together the all-purpose flour, salt, (1/4 c) sugar, and baking powder until well combined.
Using a pastry cutter or a fork, cut in the cold (grated or cubed) butter until the mixture resembles coarse crumbs.
In a separate small bowl, whisk together the milk, egg, sourdough discard, and vanilla.
Pour the wet ingredients into the dry ingredients, mixing until a shaggy dough forms.
Gently fold the dough over a few times until all the flour is incorporated. You should still see small butter pieces in the dough—don't knead it or over mix.
Roll the dough until it's about ¼-inch thick.
Use a pizza cutter, sharp knife, or bench scraper to cut the dough into 1"x1" pieces—these will be your little dough pieces for the monkey bread.