The two most important things to remember:
- Use half as much corn starch as you would flour. For example, if the recipe calls for 2 tablespoons of flour, use 1 tablespoon of corn starch. If the recipe calls for 1/4 cup of flour, use 1/8 cup of corn starch. (The same is true for other starches, such as arrowroot starch, potato starch and tapioca.)
- Don't add the corn starch directly. First mix the corn starch in a little bit of cold water until it's dissolved, and then pour the water/starch mixture (known as a "slurry") into what you're cooking, being sure to stir gently and continuously as the mixture thickens.
There are other considerations to cooking with corn starch, including:
- Cook over medium-low to medium heat, because high heat can cause lumping.
- Foods thickened with corn starch don't freeze well.
You can learn more about corn starch and its properties on the Argo & Kingsford's Corn Starch site.