Slice the slider buns in half, separating the top and bottom halves.
Place the bottom halves of the buns in a greased 9×13-inch baking dish.
Assemble the Sliders:
Layer the bottom half of the buns with half of the sliced roast beef (about 1/2 lb). Top with 4 slices of provolone cheese (or your choice of cheese).
Add the remaining roast beef on top of the cheese, then place the remaining 4 slices of cheese over the beef.
Top with the top halves of the buns.
Prepare the Butter Sauce:
In a small bowl, combine the melted butter, Worcestershire sauce, Dijon mustard (if using), garlic powder, onion powder, salt, and pepper. Stir to combine.
Pour the butter mixture evenly over the top of the assembled sliders.
Bake the Sliders:
Cover the baking dish with aluminum foil and bake for 10-15 minutes, or until the cheese has melted and the sliders are heated through.
After 10-15 minutes, remove the foil and bake for an additional 5 minutes to crisp up the tops of the buns.
Prepare the Au Jus (optional):
While the sliders are baking, heat the beef broth, Worcestershire sauce, garlic powder, salt, and pepper in a small saucepan over medium heat. Bring to a simmer and cook for 5-7 minutes, allowing the flavors to blend. Remove from heat and keep warm.
Serve:
Once the sliders are done, remove them from the oven and cut into individual servings.
Serve the sliders warm, with the au jus on the side for dipping.
