Cornstarch, which comes from the finely ground center of dried corn kernels, binds or thickens cooked foods.Use it in desserts such as puddings so they retain their creamy texture as they thicken. Cornstarch also thickens sauces, soups and gravies quickly without compromising their flavor. However, cornstarch becomes lumpy when added to hot liquids unless it's properly mixed and whisked in.
Fill a small bowl with cold water. Use the same amount of water as cornstarch. For example, if the recipe requires 2 tablespoons of cornstarch, place 2 tablespoons of water in the bowl.
Pour the cornstarch into the water slowly. Stir the mixture with a fork or small whisk as you pour the cornstarch in so lumps don't form. Stir until the mixture is fully combined.
Lower the heat on the food you are cooking so it is at a simmer. Cornstarch may separate and form lumps if added to rapidly boiling liquid.
Stir the cornstarch mixture into the food. As the mixture heats up, the food thickens.
If you mix the cornstarch and water ahead of time, stir it before adding it to the food in case it has separated.