In large bowl, add beef, Italian seasoning, salt and pepper. Mix well.

Divide mixture into 8 equal parts.

Shape each portion of the beef mixture into a patty, 8 patties total, about 4 1/2 inches in diameter and 1/4-inch thick.

Place 4 beef patties flat on a work surface.

Press 1/4 cup Mozzarella cheese into a ball with hands. Place on top of one beef patty and press flat into 3 1/2-inch-diameter disk in the middle, leaving a ring of uncovered beef around the outside. Repeat with remaining cheese and 3 beef patties.

Top each cheese-covered beef patty with one of the remaining 4 "uncheesed" beef patties. Pinch edges together to seal, creating 4 cheese-stuffed beef patties.

Add oil to a 10-inch skillet. Place over medium-high heat.

When oil is hot and shimmering, add mushrooms. Cook, stirring occasionally, until lightly browned, about 4 minutes, stirring occasionally,

Add garlic. Cook about 1 minute longer.

Remove from heat.

Heat gas or charcoal grill. (Alternately, cook in a skillet on the stovetop.)

Place patties on grill over medium heat. Cover grill.

Cook burgers 11 to 13 minutes, turning once, until meat thermometer inserted in center of patties reads 165 degrees.

During last 2 minutes of cooking, place buns, cut sides down, on grill until toasted.

Remove burgers from grill and immediately top with 1 slice of fresh Mozzarella cheese each (alternately, place the cheese on the burgers when you place the bun on the grill.)

Place the bottom buns on serving plates. Top with a cheese-stuffed burger each. Spoon about 2 tablespoons warmed pizza sauce on each burger and cover with top bun.

Serve hot.