Preheat the broiler.
In a small bowl, whisk together cornstarch and broth. Set aside.
Heat olive oil in a large nonstick skillet over medium-high heat.
Add diced onion and green pepper; sauté for about 3 minutes until tender.
Add ground beef and cook, breaking it apart, until browned, about 3 minutes. Drain excess fat.
Stir in ketchup, Worcestershire sauce, taco seasoning, salt, and pepper.
Stir the broth mixture again and pour it into the skillet. Simmer for about 3 minutes until slightly thickened.
Spoon the mixture onto hamburger buns, top with cheese, and broil until melted, watching closely to prevent burning.
Alternatively, stir the cheese directly into the meat mixture until melted.
Serve warm with chips or your favorite sides.