Spinach Garlic Meatballs Stuffed with Mozzarella

Bahan-bahan

1 lb ground beef (or a mix of beef and pork)

1 cup fresh spinach, finely chopped

3 cloves garlic, minced

1/4 cup breadcrumbs

1/4 cup grated Parmesan cheese

1 large egg

1/2 tsp salt

1/4 tsp black pepper

1/2 tsp Italian seasoning

1 cup mozzarella cheese, cut into small cubes

2 tbsp olive oil (for cooking)