Mix together beef, egg, parmesan cheese, Worcestershire sauce, garlic, salt & pepper.
Separate meat into 12 equal amounts. Taking one section at a time, make a flattened burger patty. Evenly divide turkey pepperoni over 6 of the patties. Repeat with shredded mozzarella cheese.
Top with another section of ground beef and use hands to enclose the mixture inside the patty.
Grill on both sides 5-6 minutes or until desired doneness.