01 -
In a large cast iron skillet, brown the ground beef without breaking it apart immediately. Let a deep brown crust form on about 50% of the beef before stirring and breaking it apart.
02 -
Once the beef is browned, remove it from the skillet and set aside (leaving the fat in the pan).
03 -
Add the butter, onions, bell peppers, and mushrooms to the skillet. Let them brown for 1-2 minutes before stirring, and repeat the process until they are nicely browned.
04 -
Return the browned beef to the skillet.
05 -
In a small cup, mix together the beef broth and cornstarch.
06 -
Add the ketchup, Worcestershire sauce, salt, black pepper, and beef broth/cornstarch mixture to the skillet. Stir well.
07 -
Cook for 3-5 minutes until the mixture is slightly liquidy, with about 75% of the ingredients above the liquid.
08 -
Turn off the heat and stir in the chopped Provolone cheese.
09 -
Serve the beef mixture on toasted brioche buns.