Preheat the oven to 350°F
Butter the bottom of a 9x13 baking dish with softened unsalted butter.
You can cut the bundle of rolls in half without separating them (see video).
Place the bottom half the rolls in the baking pan. Place the bottom half of the rolls in the baking dish. Top it with 6 slices each of provolone cheese, roast beef and french fried onions.
Melt the butter in a microwave-safe bowl. Add 1 tablespoon of the au Jus seasoning mix, Worcestershire Sauce, sesame seed, dried minced garlic and onion powder to the butter. This should be added. Mix until well combined.
You can coat the rolls with the mixture, but not all of it. You can save any leftovers and use them to top your steaks or bread later.
Bake the sliders covered for 15-20 minutes or until cheese is melted and tops are golden brown.
Use a sharp knife to remove the sliders.
While the sliders bake, heat the remaining au Jus mixture in a small saucepan on medium heat. Mix in 2 cups of cold water. Whisk. Bring to boil, then simmer until it thickens slightly.
Serve the sandwiches with it.