Balsamico sauce can be served in smaller quantities for seasoning as fondue sauce or grilled steak as well as roasted duck breast. Preheat a pan briefly without adding fat. Melt the sugar briefly at high temperature. Reduce the temperature. Only let the liquid sugar caramelise lightly. Add balsamic vinegar and stir. The sugar solidifies briefly and then becomes liquid again. Let the balsamic sauce boil down for 4 to 5 minutes. Mix starch flour with a little cold water. Balsamic vinegar sauce with it easily bind. It can be served warm or chilled to room temperature. Do not put balsamic sauce in the fridge, as it will thicken and then become too firm.