Preheat the oven to 425°F (220°C).
In a large bowl, combine flour, baking powder, and salt.
Add the cubed cold butter to the flour mixture.
Mix until the mixture resembles coarse crumbs.
Pour in the milk and stir until just combined.
Roll out the dough on a floured surface and cut into rounds.
Layer half the biscuit rounds on a baking sheet.
Top each biscuit round with sliced roast beef and a sprinkle of mozzarella cheese.
Cover with the remaining biscuit rounds and seal the edges.
Brush the tops with melted butter for a golden finish.
Bake for 15-20 minutes until golden brown.
While biscuits bake, combine beef broth and Worcestershire sauce in a small pot.
Once baked, allow the biscuits to cool slightly before serving.
Serve the baked biscuits with warm au jus on the side.
