I thought I read that you add cornstarch to frosting to stabilize for humidity. I actually added 1 1/2 tsp to the powdered sugar and gave it a whirl. Then I read online that you are suppose to cook it first? Why, is the cornstarch in the 10X cooked? Is there a problem adding that much to 6 cups sugar and 1 1/3 cups cocoa powder? if you do have to cook it first? won't that be difficult to incorporate into a finished frosting? Thanks
Welcome to Frosting Recipes 101.
Also called, THINK before trying something that you read about online...
COOKED cornstarch means cooked with milk or water to make a stiff pudding that is then beaten into butter/shortening and sugar to make a whipped icing.
DRY cornstarch is added to most 10X sugar (3% by weight). It can be added in the amount you tried, to control humidity. Anyway the cocoa in your recipe will do more to control humidity than the tiny amount of starch.
What works better for some people is adding dry Dream Whip topping mix as POWDER.
I think it depends on what type of frosting you are working with.
This cooked version from Rose Levy Beranbaum is to stabilize whipped cream frosting: http://www.realbakingwithrose.com/2006/03/what_is_the_best_way_to_stabil.html
This uncooked version is for buttercream: http://www.wilton.com/recipe/High-Humidity-Icing-Recipe-I
Meringue powder is another option.