FILLING
1 tablespoon olive oil
1 pound lean ground beef
1 small onion, finely diced
1 green pepper, diced
4 cloves garlic, minced
1 cup reduced sodium beef broth
1 tablespoon cornstarch
1 ½ teaspoons beef bouillon
2 tablespoons ketchup
2 tablespoons Worcestershire sauce
1 teaspoon Dijon mustard
1 tsp EACH dried oregano, dried parsley
½ tsp EACH salt, pepper, dried basil, paprika
¼ teaspoon red pepper flakes, more or less to taste
3/4 cup freshly grated sharp cheddar cheese
BUNS
6 brioche hamburger buns
softened butter or mayo for brushing (optional)
6 slices provolone cheese

INSTRUCTIONS
Preheat oven to 400 degrees F. Split buns and lay them cut side up on a large baking tray (15×21). Lightly brush the cut sides with softened butter or mayonnaise (optional for crispier/more flavorful buns). Bake for 5 minutes to toast the buns. Meanwhile you can continue with the recipe:
Heat 1 tablespoon olive oil in a large cast iron skillet over medium-high heat. Add beef, onions and bell peppers and cook until beef is browned and onions are softened, about 7 minutes. Add garlic, and sauté 30 seconds.
In a liquid measuring cup (or small bowl), whisk the beef broth, cornstarch and beef bouillon together until smooth. Add to the meat mixture followed by the ketchup, Worcestershire sauce, Dijon and all seasonings.
Gently simmer over medium heat, stirring occasionally, until most of the liquid has been absorbed, but the mixture is still a little saucy, about 5 minutes.
Stir in the sharp cheddar cheese until melted. Taste and season with salt, pepper, red pepper flakes to taste (I like more salt). Keep in mind the flavors will be diluted with the cheese and buns.
Divide mixture between the bottom toasted buns and top each with a slice of provolone cheese. Bake (leaving both top and bottoms cut side up) at 400 degrees F for 5-10 minutes or until cheese is completely melted. Top the sandwiches and serve immediately.