In a large skillet, add butter and onions. Saute until tender. Add in garlic and pepper. Cook for 1 minute until garlic is fragrant.
Remove onions from pan and set aside.
Add flour along with a couple of Tbsp of the broth to the skillet and make a paste. Add in the remaining broth, Worcestershire sauce, and salt. Bring to a boil, then reduce to a simmer for 15 minutes.
In the meat time. split hoagie rolls open and place cheese on the bottom half of the rolls. Toast until a broiler until golden brown.
Once broth is done simmering, add in beef and allow to simmer for another 5 minutes.
Top each toasted roll with some of the beef and some of the onion.
Fill ramekins of small bowls with juice from the skillet and serve with the sandwiches for dipping. Serves 4.
