The preserved onion with salted butter caramel is an essential condiment. The touch of salted butter caramel adds a little more to enhance the flavours. The onions are first finely chopped and then mixed over high heat with sugar and salted butter so that the caramel can wrap all the preparation. The preserved onions are then deglazed with the balsamic vinegar. This preparation is recommended especially for the holiday season, as an accompaniment to foie gras or pâté.