Roast pine nuts in a pan without fat and set aside. Wash the lettuce hearts and remove an outer leaf, if necessary, so that a firm stalk is formed. Carefully cut the hearts in half so that they stay together on the stalk. Heat the olive oil in the pan and fry the lettuce hearts all over. Deglaze everything with balsamic vinegar and sauté briefly. Arrange the lettuce hearts on a plate, sprinkle with the pine nuts and slice some Parmesan cheese over them.