Preheat your oven to 400°F (200°C). Lightly grease a grill griddle or regular baking sheet.
In a large bowl combine the panko breadcrumbs and milk. Allow to soak while chopping the veggies and parsley.
Add the bell pepper, onion, garlic, parsley and mushrooms to a food processor. Pulse until everything is finely minced, scraping down the sides as needed.
Add the mixture to the bowl with bread crumbs along with ground beef, Dijon mustard, liquid smoke, Mozzarella cheese, eggs, Worcestershire sauce, salt and pepper. Mix just until combined. Don't overmix or the meatloaf will be dense.
Transfer the mixture into a loaf pan, pressing down to form into a loaf. Turn out onto the prepared grill griddle.
Spread the mayonnaise over the top and sides evenly.
Bake for 45 minutes, then remove from the oven, top with provolone cheese and arrange the veggies ( optional) around the meatloaf.
Return to the oven and bake further for 15 minutes or until the meatloaf is cooked through.
Allow to rest for 10 minutes before slicing and serving.
Enjoy!