1 tablespoon oil
1 onion, diced
1 green bell pepper, diced
8 ounces mushrooms, diced
2 cloves garlic, chopped
2 pounds ground beef
1/2 teaspoon salt
1/2 teaspoon pepper
1/2 cup cheese whiz (optional)
1 teaspoon Worcestershire sauce
2 tablespoons ketchup
1 cup panko breadcrumbs (gluten-free for gluten-free)
4 ounces provolone (optional)
8 slices provolone
Heat the oil in a large pan over medium heat, add the onion, bell pepper and mushrooms and cook until tender, about 7-10 minutes.
Add the garlic and cook until fragrant, about a minute, before removing from heat.
Mix the beef, salt, pepper, cheese whiz, Worcestershire sauce, ketchup, eggs, breadcrumbs and the cooked mixture of the onions, peppers, mushrooms and garlic.
Place half of the mixture down, place the solid piece of provolone in the middle, top with the remaining mixture, seal the edges well, shape the loaf as desired and place on a baking sheet.
Bake in a preheated 350F/180C oven until cooked through, about 50-60 minutes.
Spread the sliced provolone over the top of the loaf, return to the oven and broil until the cheese has melted, about 2-4 minutes.