Butter and sugar cookies are natural vehicles for sprinkles, as the pale blonde cookies often look better when they are dressed up in some way. It is not always easy to get sprinkles to adhere to the cookie, especially if you would rather use something like chocolate jimmies or rainbow nonpareils, rather than just plain old colored sugars.
Last month’s Cook’s Illustrated offered a great tip on how to prevent the sprinkles from sliding right off of your cookies – without having to jam them down into the surface of the dough, deforming the cookie’s shape. They suggest lightly brushing the surface of the shaped cookie with water, then sprinkling on the sprinkles. Butter cookie dough is especially dry due to the high amount of butter in it, and the water provided just enough stick without altering the finished cookie at all.
CI also tried using beaten egg, oil/cooking spray and corn syrup for comparison. The egg and cooking spray worked just as well as the water, but corn syrup cause the cookies to become extra dark and crunchy on top. In the end, they opted to recommend the water method even over the oil and egg of out sheet convenience.
via book of joe