Cornstarch has long been a favorite thickening agent, especially in Asian Cuisine where it is used to thicken the natural sauce that occurs in the bottom of the wok when stir frying.  corn starch is also used throughout cooking to thicken or add texture to soups and sauces.  When using cornstarch it must be diluted in a cold liquid and then added to the sauce of soup that is almost at the boiling point.  While adding the starch the product must be constantly stirred to avoid lumps of congeals starch and sauce.  The soup or sauce will return to its original transparency and appearance as the starch cooks out.

Dilute cornstarch with a liquid that will enhance or add to the flavor of the sauce like cold stock, soy sauce, wine, or milk instead of water.

Cornstarch congeals when cold more than other starches like arrowroot.