How to make it
Preheat oven to 400°F.
Pour milk over the bread in a bowl so bread absorbs the milk. In a separate bowl, mix onion, egg, beef, parsley, cheese, garlic, sriracha, salt, and Worcestershire sauce together. Gently fold in the bread and milk combination. Do not overmix.
Divide the mixture into 4 components (¼ pound just about every) and kind just about every a person into a meatball. Depress a cube of mozzarella into the center of every meatball, then deal with up.
Space meatballs on a greased baking sheet so they do not contact. Bake meatballs for 30 minutes.
Although meatballs are cooking, simmer tomato sauce. Once meatballs are cooked, position in simmering tomato sauce for 10 minutes. Add a minor further cheese to the best. Serve.