Add the ground beef to a large cast iron skillet and brown on medium-high heat until a deep brown crust appears before breaking the beef apart.

Stir the ground beef and brown until a deep crust appears on about 50% of the beef.

Remove the beef (you can leave the fat) and add the butter, onions, bell peppers, and mushrooms.

Let brown for 1-2 minutes before stirring, then let brown for another 1-2 minutes before stirring again.

Add the beef back into the pan.

In a small cup, mix the beef broth and cornstarch together.