Old flour makes cruddy sugar cookies.
Here's how I came to this realization. For Christmas, I made my boyfriend the cutest sugar cookies.
Aren't they adorable? I made them late at night on Christmas Eve Eve so that he wouldn't know about them until Christmas. I painstakingly rolled out the dough on Christmas Eve morning and had the darnedest time getting that green sugar to stick. As your eyes will tell you, they looked great when they were done.
But they tasted like crap. Or, more accurately, they tasted like flour. I blamed the ratios in the sugar cookie recipe, which was part of the problem, but it wasn't the whole problem. As I discovered when I made waffles a few weeks later, our flour was old, and therefore, not good.
Last night, I made new cookies. (There is no picture because they were significantly less twee.) I used new, unbleached all-purpose flour (and a less flour-heavy recipe), and they turned out great.
I realize this may not be the discovery of the century, but it certainly made me think twice about using whatever ingredients are lying around.