In my recipes I usually give a choice of thickeners: arrowroot, potato starch, or cornstarch. I realize that cornstarch is the one most available in the American home, and in fact the one used in certain pastry preparations in France. But for cooking, and especially sauce making, I, along with most French chefs, prefer the use of arrowroot or potato starch. Both produce sauces that are brighter and of better consistency than those made with cornstarch. Arrowroot is found in the spice section of the supermarket, and potato starch is normally found in the kosher or foreign specialty section.