Prepare the marinara sauce by heating olive oil in a pan over medium heat. Sauté the chopped onion for five minutes, then add garlic, crushed tomatoes, bay leaf, black pepper, and fresh parsley. Let it simmer on low to medium heat for 20-30 minutes while you make the meatballs.
For the meatballs, preheat your oven to 400°F. Line a half sheet pan with parchment paper.
In a large bowl, combine the meats, egg, and seasonings.
Take a golf ball-sized portion of the mixture, place a mozzarella cube in the center, and shape it into a meatball, ensuring the cheese is fully enclosed.
Bake for 15-20 minutes until cooked through. Serve with marinara sauce and garnish with fresh parsley or basil.
Notes
Feel free to adjust the seasonings and herbs to your taste!