There's a chocolate chip cookie recipe I want to try, but it calls for an ingredient I've never seen in cookie recipes. Just 1 tsp. of corn starch is needed. Not having any in my pantry, I looked online for substitutions, but they all have to do with thickening sauces (like arrow root, flour & mashed potatoes), and nothing to do with baking. Would any of you bakers know the purpose of corn starch in baking?