Preheat the oven to 350°F (175°C).
In a small mixing bowl, whisk together the melted butter, Worcestershire sauce, Dijon mustard, garlic powder, and a pinch of salt and pepper.
Place the slider buns in a 9x13-inch baking dish, keeping the buns connected.
Layer the bottom half of the buns with slices of roast beef, followed by a slice of provolone cheese for each bun.
Place the top half of the buns on top of the beef and cheese layers.
Pour the butter mixture evenly over the top of the buns.
Cover with foil and bake for 15 minutes, then remove the foil and bake for an additional 5-7 minutes, until the cheese is melted and the tops of the buns are golden brown.
While the sliders bake, heat the beef broth in a small saucepan over medium heat, allowing it to simmer.
Remove the sliders from the oven and let them cool for a few minutes before serving.
Serve the sliders with the warm beef broth for dipping. Garnish with chopped parsley if desired. Enjoy!