Preheat broiler.
In a small bowl, whisk together the cornstarch and broth. Set aside.
Heat the oil in a large nonstick skillet over medium high. Add the onion and peppers; sauté 3 minutes until tender. Add in the beef and continue to cook, breaking it up and browning, for another 3 minutes. Drain off fat.
Stir in the ketchup, Worcestershire, taco seasoning, salt, and pepper.
Give the broth and cornstarch a quick stir and add it to the skillet; simmer for about 3 minutes, stirring occasionally, until mixture thickens slightly.
Scoop some mixture onto buns, top with 1/4 cup cheese, and stick under the broiler until melted-keep a close eye, so nothing burns! (Alternatively, you can simply add the cheese in with the meat mixture and stir until combined and melted.)
Serve warm with chips and enjoy!