Chef Bobby's beef sliders

INGREDIENTS 8 tbsp. butter, divided 1 large onion, thinly sliced 1 ounce of Good Cognac 2 sprigs, plus 1/4 teaspoon fresh thyme Kosher salt Freshly ground black pepper 16 slider buns, halved 2 lb. Your Choice of Sliced Seared Beef Tenderloin , Skirt Steak or Shaved top round 20 slices provolone cheese 1/4 tsp. garlic powder 1 tbsp. clove garlic, minced 1 1/2 c. low-sodium beef broth 1 tbsp. Worcestershire sauce 2 Fresh sprigs of Rosemary DIRECTIONS 1. Preheat oven to 350°. In a large skillet over medium-high heat, melt 2 tablespoons butter. Add onion and thyme sprigs and season with salt and pepper. Cook, stirring occasionally, until caramelized, about 15 minutes deglaze onions with cognac and lean back so you don’t catch fire!!!. Discard thyme. 2. Place bottom halves of slider buns on a large baking sheet and top with roast beef, provolone cheese, caramelized onions, and slider bun tops. 3. Melt 2 tablespoons butter and brush on top of buns. Sprinkle with garlic powder, coarse salt, and parsley and bake until cheese is melty and sliders are warmed through, 10 to 15 minutes. 4. Meanwhile, make au jus: Add remaining 1 tablespoon butter to same skillet and melt over medium heat. Add garlic and cook until fragrant, 1 minute, then add beef broth, Worcestershire, Rosemary and thyme and season with salt and pepper. Simmer until slightly reduced, 10 minutes. 5. Serve sliders with au jus for dipping.