Melt 2 tablespoons butter in a large cast iron skillet.

Add the ground turkey and brown until full cooked (ground turkey should reach 165 degrees F.)

Remove the turkey (you can leave the fat) and add the remaining 2 tablespoons butter and the 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 turkey back into the pan.

In a small cup mix the beef broth and cornstarch together

Add the ketchup, Worcestershire sauce, salt, black pepper, beef broth/cornstarch mixture into the pan.

Cook until the mixture is only slightly liquidy (about 75% of the mixture is above liquid), about 5 minutes.

Turn off the heat, add in the provolone cheese.

Served on toasted brioche buns.