Heat a large skillet over medium heat. Add the ground beef to the skillet and break apart with a fork. Cook the ground beef until brown and a deep crust begins to form.
Continue cooking until no longer pink.
Using a slotted spoon, transfer the beef to a bowl and drain off all but two tablespoons fat.
Add the onions and bell peppers to the skillet.
Cook for 1-2 minutes before stirring, then toss the vegetables and continue cooking for an additional 1-2 minutes until softened and beginning to caramelize.
Return the beef back to the skillet.
In a small bowl, whisk together the beef broth and cornstarch.
Add the ketchup, Worcestershire sauce, salt, black pepper, garlic powder, beef broth/cornstarch mixture to the skillet and stir.
Simmer the sloppy joe mixture for 5-8 minutes or until beginning to thicken.
Remove the skillet from the heat and stir in the provolone cheese.