Heat a saut? pan over medium heat. Crumble ground beef and season with salt and pepper, then cook until browned, about 5 minutes. Remove from pan and set aside. Drain excess grease from the pan, if necessary.

Add butter to the pan. Once melted, add onion and bell pepper and saut? until vegetables begin to brown and onions turn translucent, about 4-5 minutes.

Reduce heat to low, then return ground beef to the pan. Add garlic powder, Worcestershire sauce, and beef broth, scraping the bottom of the pan as you incorporate your ingredients. Cook for about a minute.

Add cornstarch and stir until dissolved, about a minute. If beef looks dry, add 1-2 tablespoons of water.

Remove from heat. Top meat mixture with cheese slices and allow to set for 1-2 minutes, or until melted. Remove from heat, spoon onto rolls, and serve immediately.