Let your slow cooker work its magic with Italian-style meatballs made even more savory by the addition of ooey gooey mozzarella cheese. Perfect with alfredo or marinara sauce, these bite-size wonders are definitely worth trying. So how are they made? Mix together ground beef, egg, egg yolk, bread crumbs, onion powder, garlic, Italian seasoning and some salt and pepper in a bowl. Roll the mixture into balls, adding a small piece of chilled mozzarella in the center. Cook the meatballs in your slow cooker for one to two hours (on high) or three to four hours (on low). Or you can bake them in an oven for 15 to 20 minutes (at 400 degrees).