A great stand-in ingredient that is used to thicken gravy, sauce or custard is cornstarch. Flour is the firsthand pick by most cooks but just the same, cornstarch delivers the same result. The only difference – cornstarch dissolves a lot easier and you don’t expect to see an opaque mixture.
For every two tablespoons of all purpose flour in a recipe, substitute one tablespoon of cornstarch. Whichever you prefer to use, just ensure that you bring the liquid to a full rolling boil. Normally, one minute is all you need to boil the mixture so that the starch in the flour or cornstarch thicken and expand properly.