Preheat the oven to 400°F (200°C).

Roll out the puff pastry on a floured surface.

Spread Dijon mustard over the rolled pastry.

In a mixing bowl, combine the sliced beef, garlic powder, onion powder, and season with salt and pepper.

Layer the seasoned beef over the mustard-coated pastry.

Sprinkle shredded provolone cheese over the beef.

Cover with the second sheet of puff pastry, sealing the edges with a fork.

Cut the top pastry layer into squares before baking.

Bake for 20-25 minutes, until golden brown.

While baking, prepare the au jus by heating beef broth and adding Worcestershire sauce.

Let the squares cool for a few minutes before serving with au jus.

Garnish with chopped parsley if desired before serving.