Preheat your oven to 375°F (190°C).

In a large bowl, combine ground beef, breadcrumbs, Parmesan cheese, parsley, egg, minced garlic, onion powder, salt, pepper, and oregano. Mix until well combined.

Shape the mixture into meatballs, about 1 inch in diameter, and place them on a baking sheet.

Place the meatballs in the preheated oven and bake for 20-25 minutes, or until they are cooked through and browned.

While the meatballs are baking, place the cubed potatoes in a large pot and cover with water. Bring to a boil and cook for 15-20 minutes, or until fork-tender.

Drain the potatoes and return them to the pot. Add milk, butter, salt, and pepper. Mash until smooth and creamy.

In a large baking dish, spread the mashed potatoes evenly on the bottom. Place the baked meatballs on top of the mashed potatoes.

Sprinkle the shredded mozzarella cheese over the meatballs.

Return the baking dish to the oven and bake for an additional 15-20 minutes, or until the cheese is melted and bubbly.

Remove from the oven and garnish with chopped fresh parsley before serving.