Pre-cooked. Ready to heat & serve. Polenta is a traditional Italian dish made from boiled cornmeal, which can be served as a side dish or used as a base for various recipes. Instant polenta in a tube is a convenient and quick alternative to traditional polenta, which requires time and effort to cook. The pre-cooked polenta is typically made by mixing cornmeal with water or milk, then cooking it until it thickens and becomes creamy.