Put the ground beef, Parmigiano cheese, bread crumbs, nutmeg, parsley, salt, pepper, milk, and extra-virgin olive oil in a mixing bowl. Mix all the ingredients together well.
Heat a grill.
Scoop the mixture into the palm of your hands and form a meatball. Then flatten out the meatball so that it resembles a meat patty. Place the meat patty between 2 lemon leaves. Repeat the process with the remaining beef mixture.
Cook the patties on a hot grill for a few minutes on each side. As they cook, the oils from the lemon leaves will infuse the meat patties with lemon flavor. Use tongs to securely lift and turn over each meat patty so that it remains sandwiched between the two lemon leaves as it cooks. Transfer the meat patties, still sandwiched between the lemon leaves, to a serving platter and serve immediately.
Your guests should discard the lemon leaves and eat the meat patties.