Preheat oven to 400°F. Line a large rimmed baking sheet with a piece of aluminum foil. Spray the foil with olive oil cooking spray. Set aside.

In a large mixing bowl, combine together the lean ground beef, mild Italian sausage, egg, breadcrumbs, grated parmesan cheese, finely minced yellow onion, half & half, grated garlic, Italian seasoning blend, salt, and black pepper. Use your hands or a wooden spoon to ensure all ingredients are fully combined. Do not overmix.

Using a 2-inch cookie scoop, portion out 15 meatballs and place them onto a plate.

Gently flatten one meatball into a disc about 3½ inches wide.

Place one mozzarella cheese cube in the center of the flattened disc. Carefully fold the sides up and around the cheese cube, then gently roll the meat into a ball shape. Ensure no cheese is exposed.

Place the mozzarella cheese-filled meatball onto the prepared baking sheet. Repeat with remaining meatballs.

Bake for 20-25 minutes, or until lightly browned and cooked through with no pink remaining. You can cut one open to check for doneness at 20 minutes.

Remove meatballs from the oven and let them rest on the baking sheet for five minutes.

While the meatballs are resting, warm the marinara sauce in a medium skillet over medium-low heat.

Spoon about ½-¾ cup of warm sauce onto a serving plate, add the meatballs, and top with another ¾ - 1 cup of sauce.

Garnish with a sprinkle of grated parmesan and fresh chopped parsley.