Preheat your oven to 400°F and line a baking sheet with parchment paper.
In a large bowl, whisk your flour, baking powder, garlic powder, and salt. Add the cold, cubed butter. Use a pastry cutter or your fingers to work the butter into the flour until it looks like coarse crumbs with some pea-sized chunks remaining.
Toss the shredded cheddar into the flour mixture so it’s well-coated.
Stir in the sourdough discard and milk. Mix gently with a spatula just until a shaggy dough forms. Do not overmix, or you'll end up with hockey pucks instead of fluffy biscuits!
Use a large spoon or a measuring cup to drop mounds of dough (about 60–70g each) onto the baking sheet. Bake for 12–15 minutes or until the tops are golden brown.
While they bake, whisk together the melted butter, garlic powder, and parsley. As soon as the biscuits come out of the oven, brush them generously with the garlic butter.
