It's always good to get to see presentations about cookie techniques, because either it will help to solidify something in my mind or, even better, will teach me something new. A problem I never really considered before was a crumbling cookie. If you make a cookie that has to travel some distance, you'll find that your average cookie recipe will leave you with something that cannot survive bumps and jolts without turning from a round confection to a pile of crumbs and bits.
I was watching an IACP presentation by Shirley Corriher, author of BakeWise and CookWise , and also Food Scientist Extraordinaire on Good Eats. During her presentation, she talked about how to keep cookies from crumbling. The problem comes in because all of the sugar in the cookies absorbs all of the water, keeping the water from combining with the flour to make gluten. Exacerbating that lack of water due to sugar is a literal lack of water, as most cookie recipes have very little water-type liquid added to them. To make matters worse, all of the butter in the cookies will coat the flour, thus preventing whatever water may have been added which had not already joined up with the sugar unable to get to the flour. It makes for a crumbly cookie, because there are no long chains of gluten to ensure a structure that can hold up under pressure.
The solution is devilishly simple: take a cup of the flour that is in your cookie recipe and, before anything else, mix it with a few tablespoons of water until it forms a dough (exact amount of water depends on the type of flour and so on, but just add as much as you need and no more). Make your cookies as normal, but add this dough in at the end. Depending on how much you kneaded the dough, you will give extra strength and body to your cookies, and you will be able to control the texture by kneading it more if you want more chewiness to the cookie.
One of the added benefits of this method is that, because the water is all tied up making gluten in the flour, it's not going to throw off your cookie recipe's balance. The water isn't going to be released into the cookie, so you only have to worry about how much extra body you are giving your cookie and not wether the cookies will become a soggy mess.
Of course, you don't want to do this with a shortbread cookie, because the very definition of a shortbread cookie is that you don't have long gluten chains. I mean, you can make what would be a shortbread cookie with this recipe, but it won't be shortbread any more.