French Dip Sliders

Name: French Dip Sliders
Prep time: 10 min
Cook time: 20 min
Total time: 30 min
Cuisine: American
Ingredients: 2 tablespoons unsalted butter (softened); 12-count package Hawaiian sweet dinner rolls (see note 1); 1 pound deli roast beef (see note 2); 12 slices provolone cheese (divided); 1-1/2 cups crispy fried onions (optional); 8 tablespoons unsalted butter; 1 packet au jus gravy mix; 1 teaspoon Worcestershire sauce; 1 tablespoon sesame seeds; 3/4 teaspoon dried minced garlic; 1/2 teaspoon onion powder