For More Tender Cookies, Reach For This Tangy Ingredient
Cookies not only come in all shapes and sizes but all sorts of textures, too, from thin and crunchy to soft and squishy. If you really want your cookies as tender as can be, though, try adding some acid — lactic acid, that is, in the form of sour cream. The acid helps keep gluten from developing, and gluten, as you may recall, is the stuff that gives baked goods body and structure. It's all very well to have a dense, gluten-rich bread, but excess gluten in cookies can be too much of a not-so-good thing.
Like the equally acidic buttermilk, sour cream can be added to cakes to make them moister, and it also makes for a great secret brownie ingredient, as well, especially if you prefer them cakey rather than chewy. Sour cream also makes for cookies that are extra rich as well as soft and tender because it adds to the fat content and fat = flavor. The slight tang of the ingredient itself, however, really won't impact the taste of the cookies much, if at all, so there's no need to worry if you don't want your sugar cookies to taste sour.
This sour cream alternative has all of the tang with none of the moisture
The main drawback to adding sour cream to your cookie dough is that if you're not an expert recipe developer, it's really only best to do so if you find a cookie recipe that actually calls for the stuff, like our old-fashioned sour cream sugar cookies. Just plopping a few spoonfuls of such a wet ingredient into your dough is likely to throw off the liquid-to-dry ratio and may result in cookies that ooze all over the pan. There is another tangy ingredient, though, that can easily be swapped into most standard cookie recipes: cream of tartar.
Cream of tartar, which is made from the gunk scraped out of wine casks, is often used to stabilize whipped cream or egg whites or help keep sugar from crystallizing. It can have leavening properties, too, which is another trait it shares with sour cream. Cookies made with the former may not require baking powder, but you can replace this leavening agent in just about any cookie recipe with ¼ the amount of cream of tartar combined with an equal amount of baking soda. The best part of using cream of tartar in your cookies, though, is that its acidic nature inhibits gluten from forming, just as sour cream does, thus helping to give cookies a soft and tender texture.