How to thicken with cornstarch
Whether you’re making a soup, stew, gravy, or even sauce, more than likely you will be in need of a thickening agent. Granted one could try to boil said dish to the point where it might thicken on its own, but this is time-consuming and not always effective. For most chefs and cooks out there, the choice is cornstarch.
Cornstarch is as its named. It’s the milled starch made from slightly fermented corn. While it’s primary use is for thickening liquid food items, it can also be used somewhat like flour in regards to coating. You’ll see it used often in this regard in Asian cuisine.
What makes cornstarch such a good pick for thickening is in how it’s flavorless, and it will not change the color of a gravy, soup, or sauce you put it in. With other choices such a flour, you might end up lightening the color of your final dish as well as changing the overall flavor. Some soups and stews do call for a flour-based roux, but only because the after-effect is desired.
Thickening with Cornstarch
When using cornstarch as a thickening agent, you can’t just lob a spoonful into your soup or stew and think it’ll work. You’ll instead end up with a thin liquid and a glob of white slime swimming around in it.
Cornstarch is similar to flour in that heat will cause it to expand, hence how it chemically thickens. You should take one tablespoon of cornstarch and mix it in 1/4-1/2 cup of cold tap water. I’ll usually mix it in a measuring cup so I can easily pour it.
Stir thoroughly to make sure the cornstarch is fully dissolved into a slurry. You want to end up with a cup of white, milky liquid. When ready, carefully pour and fully stir the slurry into your soup, stew, or whatever you want to thicken. I’ll usually pour in half of what I make, stir, wait a few minutes, and then add more if I think the final product isn’t thick enough.
And that’s it. If you did it correctly then you should end up with a thicker liquid that tastes the same as it did before you thickened it.