Preheat your oven to 425°F (220°C).
In a large bowl, mix together the flour, baking powder, salt, and black pepper.
Cut in the cold butter until the mixture resembles coarse crumbs.
Stir in the milk until just combined; do not overmix.
Turn the dough onto a floured surface and knead gently a few times.
Roll out the dough to about 1-inch thick and cut into rounds.
Place the biscuits onto a baking sheet lined with parchment and bake for 12-15 minutes.
While the biscuits are baking, prepare the au jus by combining beef broth, Worcestershire sauce, and garlic powder in a saucepan over medium heat.
Once the biscuits are done, let them cool slightly, then slice in half horizontally.
Layer the sliced roast beef inside the biscuits and serve with warm au jus for dipping.