PREHEAT oven to 400ºF. Line a baking sheet with aluminum foil.
CUT mozzarella into small, square chunks; set aside.
COMBINE all ingredients (except salt and pepper) in a large bowl and mix together using your hands or a large wooden spoon. (You can also use a stand mixer with the paddle attachment to combine ingredients.)
SCOOP meatball mixture using a small cookie scoop, or by scooping similar-sized amounts with a table spoon; place onto prepared baking sheet.
PLACE a mozzarella square in the middle of each meatball, then roll each one in your hands to hide the cheese and smooth out the meat. Once you have rolled each meatball, season with salt and pepper.
BAKE for 20 minutes. If you cut into a meatball and there is still pink inside, bake again in 2-minute increments until cooked through.