Q. We like crisp cookies, so I set out on a quest to find out what makes them crisp. One of the suggestions on a baking website was to use egg yolks instead of the whole egg. If the recipe calls for two eggs, would you use two egg yolks? What do you add to make up for the moisture the whites provide?
Most cookie recipes call for one egg, so you could use two yolks without much loss of moisture. But I think eggs may be the wrong culprit. While some baking sites do suggest using yolks only for crispness, many more disagree with that theory — with good reason. Egg whites generally give crispness and dryness to the final texture of baking goods. Egg yolks contain most of the egg’s fat, so they contribute richness and a softer, cakier texture.
Instead, I’d look at two other factors that are involved with crispness. The first is the sugar. Brown sugar is more moist, while white sugar causes dryness. So you want a recipe that has more white than brown sugar. A cookie that has all brown sugar is going to be softer after it’s baked.
Second, make sure you’re using butter instead of shortening. Butter makes cookies crisp while shortening makes them softer.