Preheat and prep: Heat your oven to 350°F (175°C). Line a 9x13-inch baking pan with parchment or lightly grease it. Keep the rolls attached as a sheet and slice them horizontally to create a top and bottom slab.

Make the au jus base: In a saucepan over medium heat, melt 1 tablespoon butter. Add minced onion and cook 2–3 minutes until softened. Stir in garlic for 30 seconds.

Build the au jus: Add beef broth, Worcestershire, soy sauce, thyme, bouillon (if using), and a few grinds of black pepper. Simmer 10–12 minutes to reduce slightly. Taste and adjust salt only if needed. Keep warm.

Make seasoned butter: Melt remaining 5 tablespoons butter. Stir in onion powder, a pinch of black pepper, and poppy or sesame seeds if using.

Assemble the sliders: Place the bottom slab of rolls in the pan. Lay half the cheese in an even layer. Drape the roast beef across in loose folds for height and juiciness. Top with remaining cheese. Cap with the top slab of rolls.

Brush and bake: Brush the tops generously with the seasoned butter. Cover the pan loosely with foil (tent it so it doesn’t stick). Bake 15 minutes, then uncover and bake 7–10 minutes more until the cheese is melted and the tops are golden.

Warm the beef (optional): For extra moisture, dip a few slices of the roast beef quickly in the hot au jus before layering. Don’t soak too long or the sliders can get soggy.

Rest and slice: Let the sliders rest 5 minutes to set. Cut along the roll lines with a serrated knife.

Serve: Ladle the hot au jus into small bowls. Add a little creamy horseradish on the side if you like a kick.