Pre-heat the oven to 180C(360 F).
In a large bowl, place the ground beef then add the breadcrumbs, grated onion, beaten egg, salt, cumin, ground black pepper, and minced parsley leaves. Combine all very well.
With wet hands take a piece the size of a large walnut and roll. Continue until all meatball mix is finished and set aside.
Heat the vegetable oil in a pan and fry the wedge-cut potatoes first. After they are fried; place them onto the paper towel to remove excess vegetable oil and set them aside.
Fry all meatballs and distribute them to each clay pot evenly.
Place the fried potato wedges 1 by 1 between each meatball in the clay pots and then set them aside.
For the sauce; place the butter, olive oil and tomato paste into a saucepan and cook for about 3 minutes at medium heat. And then; add the minced garlic, pinch of salt, and peeled cube cut tomatoes for about 5 more minutes.
Remove the sauce from the heat and then pour the sauce evenly on the top of meatballs and potato wedges.
Place the clay pots into the oven tray and cook for 20 minutes.
After 20 minutes, remove the oven tray out add the grated mozzarella cheese on top of each clay pot, and cook additional 5 more minutes.
Serve.