Prepare the Au Jus: In a small saucepan over medium heat, mix low-sodium beef broth with Worcestershire sauce, garlic powder, onion powder, and black pepper. Heat until aromatic, about 3-4 minutes.

Sauté the Beef: Add the thinly sliced roast beef to the au jus mixture. Warm it through for 2-3 minutes, letting the beef soak up those delicious flavors.

Assemble the Sandwich: On one slice of sourdough bread, layer provolone cheese, then add the sautéed roast beef. Top it with another slice of cheese and close it with another piece of bread.

Grill: In a skillet over medium-low heat, melt the unsalted butter. Grill the sandwich until it's golden brown and crispy on both sides, about 3-4 minutes per side.

Serve: Cut the sandwich in half and enjoy it hot with your flavorful au jus on the side for dipping.