Preheat oven to 325 degrees F (170 degrees C).
In a 9x13 baking dish, layer the onion slices on the bottom of the dish. Season with sugar, 1 teaspoon salt, 1 teaspoon pepper and toss to coat slices in seasoning.
In a small bowl, use a fork to mix butter, 1 teaspoon salt and 1 teaspoon black pepper with the pressed garlic to make a 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 on top of onion slices in baking dish or dutch oven.
Pour in beef broth or consomme, then put into the oven, uncovered, for 2 hours. Tent with aluminum foil (or cover with lid) after 2 hours, for 30 minutes to 1 hour, until chuck roast is tender, meaning that you can pry the meat apart fairly easily with a fork. I personally serve this sliced in my sandwiches, so I don't cook it until it's falling apart like a pot roast; however, it can definitely be served at that stage and be absolutely delicious.
Pull roast out; slice the meat on a cutting board. Use a sieve to strain the onions from the jus and save both the jus and onions separately.
In hoagie rolls, layer slices of cheese, onions, and meat. Place on baking sheets and put into the still warm, turned off oven or at a low temperature. Melt the cheese, then remove from oven. (Yes, microwaving works, too. Just enough to melt the cheese!)
Serve hot with jus in a side container to dip into.