Cornstarch is a naturally gluten-free thickener derived from the endosperm of the corn kernel. It works well in sauces and soups but is not a good substitute for flour in baked goods.
For the best consistency, mix cornstarch with cold water to form a paste or slurry that can be added to liquid-based recipes. Recipes generally require about half as much cornstarch as flour. Cornstarch also works best when combined with a dish toward the end of cooking, since it tends to break down faster than flour. After pouring the cornstarch mixture into the hot liquid, constantly stir the sauce, gravy, custard or soup over medium heat until the texture becomes smooth and creamy. Dishes made with cornstarch are best eaten fresh because the consistency can be altered by chilling and reheating.