Slice the onion into 1/4 inch rounds.

Keeping the rounds intact, place them in the bottom of the slow cooker.

Whisk together beef broth, soy sauce, worcestershire sauce, mustard, and garlic. Add to the slow cooker over the onions.

Salt and pepper both sides of the roast and place on top of the onions.

Cook on LOW for 6 to 7 hours until beef is tender and falling apart.

Once meet is done cooking, transfer the roast to a cutting board and shred using two forks.

Remove the onions from the slow cooker and set aside.

Remove the juice from the slow cooker and strain the juice into a large "defatter" measuring cup and get rid of the oil that collects on top.

Return the shredded roast to the slow cooker with a few tablespoons of the juice to moisten and set slow cooker to WARM.

Heat the broiler.

Place the split sandwich rolls on a lined baking sheet and toast for 1 minute or just until the rolls begin to brown.

Scoop the shredded beef onto the bottom of the rolls and top with cheese.

Return to broiler until the cheese is melted.

Top sandwiches with onions and serve with small bowls of juice.