Do the prep. Preheat the oven to 350°F or 177°C. Spread the softened butter on the bottom of a 9×13 inch baking dish.
Assemble the sliders. Place the bottom half of the rolls into the baking dish. Top with 6 slices of provolone cheese, roast beef, french fried onions, and the remaining 6 slices of cheese. Add the top half of the rolls.
Make the sauce. In a small bowl melt the butter in the microwave. Mix in 1 tablespoon of the Au Jus seasoning, Worcestershire sauce, sesame seeds, dried minced garlic, onion powder. Whisk until well combined. Top the rolls evenly with this mixture.
Bake. Place into the oven and bake for 15 minutes or until the cheese is melted and the rolls are golden brown.
Make the au jus. While the sliders are baking, take the remaining Au Jus mix and place in a small saucepan over medium heat. Add 2 cups of cold water and whisk. Bring to a boil and then reduce heat and simmer until slightly thick. Serve with the sliders.