Preheat the grill to high heat, about 450°F to 500°F. A fully heated grill creates a strong sear and helps prevent the patties from sticking.

Melt the butter in a small microwave safe bowl for about 20 seconds. Stir in the garlic seasoning with herbs until smooth and evenly combined. Set aside.

Place the pepperoni slices between two layers of paper towels, making sure they do not overlap. Microwave for 15 seconds until slightly curled and glossy with released grease. Set aside to cool and crisp.

Divide the ground beef into four equal portions and flatten slightly. Place a small amount of Italian sausage in the center of each portion, then gently fold the beef around it and reshape into thick patties. Season both sides with salt and pepper.

Reduce the grill heat to medium high, around 400°F. Grill the patties for 2 to 3 minutes per side until dark grill marks form and the centers remain juicy. Move briefly to indirect heat if flare ups occur.

Brush the cut sides of the buns with the garlic butter. Grill cut side down for about 1 minute, just until lightly toasted with clear grill marks.

Place each patty on the bottom bun and spoon a small amount of pizza sauce on top. Add shredded mozzarella and crispy pepperoni. Place the burgers on foil, close the grill lid, and cook for 1 to 2 minutes until the cheese is fully melted and bubbly. Broiling indoors is also an option.

Sprinkle with Parmesan cheese, add the top buns, and serve immediately while hot and melty.