Start by cutting the cabbage into small strips and transfer to a bowl.
Grate the onion and transfer it to the bowl with the cabbage, add the ground beef, the egg and season with salt and black pepper. Mix it all together very well until combined. Set aside.
Into a glass baking dish, add 1 drizzle of olive oil or oil, spread very well, greasing the whole baking dish, set aside.
Get some of the meat, round it by hand into a ball and place it on the baking dish, repeat this process until you've used up all the meat.
Cover the baking dish with aluminum foil and take to a preheated oven at 200°C (392°F), cook for 40 to 60 minutes.
Note: Cooking time may vary depending on the power of your oven.
Into a bowl, add the mayonnaise and the mozzarella cheese, mix very well and set aside.
After the meat has cooked through, take it out of the oven and remove the aluminum foil. Get the cheese mixture and pour over each meatball.
Return it to the oven and leave for 20 to 30 minutes.
Serve.