Preheat oven to 325 degrees F (165 degrees C).

In a 9x13 baking dish or large dutch oven, layer the onion slices on the bottom of the dish. Season with the sugar, 1 teaspoon salt, 1 teaspoon pepper and toss to coat onion slices in seasoning.

In a small bowl, use a fork to mix the butter, 1 teaspoon kosher salt, and 1 teaspoon black pepper with the pressed garlic to make a garlic paste. Use the rest of the salt and pepper to season the meat generously on each side, then rub the garlic paste over each side of the roast. Place the seasoned chuck on top of the seasoned onion slices in your baking dish or dutch oven.

Pour in beef broth then put it into the oven, covered with aluminum foil or with oven-safe lid, for 2 hours. Remove the lid and cook for another hour until chuck roast is tender and barely holding together.

Pull the roast out; slice and shred the meat on a cutting board. Use a fine mesh sieve to strain the onions from the jus; save both the au jus and onions separately.

In the sandwich rolls, layer slices of cheese, onions, and meat. Place on baking sheets and put into the oven on a low broil. Melt the cheese for a few minutes, then remove from oven.

Serve with the jus in small bowls on the side to dip into.