莫莉·富尔顿asks via Twitter:

Hi, Molly,

There are usually a couple of reasons that cookies will go flat. Let’s take a look at the mechanics of a cookie first, then we’ll get into what likely happened with yours.

A cookie generally starts out with some sugar creamed into fat of some sort. Creaming, in this context, means mixing in thoroughly, enough so that the sugar essentially disappears and the butter becomes visibly lighter in color and fluffier. This will make tiny holes in the fat, which, when baked, will become slightly-larger holes in the cookie. This change from tiny holes to slightly-larger holes is what provides some of the rise.

之后，您将混合干燥和湿的成分。就饼干而言，您不会用湿食物使用太多。通常，您会有一些鸡蛋，通常是调味的提取物。您很少需要更多的液体。干成分由面粉和某种化学酵剂（小苏打或发酵粉）组成。酵徒是您将获得其余电梯的地方。

Depending on your chemical leavener, you will either get bubbles created immediately when it’s added to liquid, or you’ll get bubbles when it gets to a certain temperature. For all the details on leaveners, check out my article describingbaking soda and baking powder。

最后，当您烘烤饼干时，会发生许多变化：脂肪融化，酵徒激活，空气膨胀，淀粉凝胶化，淀粉套装和氨基酸棕色。这些发生的速度有多快会影响您的cookie。理想情况下，您希望酵徒在脂肪仍然有些坚固的同时激活，从而有机会扩展空气，然后当面粉中的淀粉凝胶化然后凝固时，以确保所有这些都在适当的时间内发生。最后，马利亚德的反应应导致您的饼干变成金黄色和美味。如果似乎要跟踪很多，请不要担心记住它。我只希望您对发生的事情有一个了解，因此建议将有意义。

What’s most likely happening with your cookies is that your butter is melting before the other reactions have a chance to happen. This will happen if your butter was too warm before cooking. If your butter is too soft, then right on putting it in the warm oven, it will just melt the rest of the way and your cookies will spread. Then, by the time the other reactions happen, it will be too late. The way to fix this is to ensure that your cookies are chilled before you cook them, either by resting the dough in the fridge for a few hours or overnight before shaping and baking, or by forming the cookies then cooling the cookie sheet in the fridge for an hour. For more detail on keeping your ingredients at the right temperature, check out my article on成分温度，尤其是鸡蛋和黄油。

If you used a different fat, such as shortening or lard, then you would have a lot more leeway on the temperatures, and you would likely get taller cookies. The flavor would be very different. Especially with the lard.

Another possibility is that your oven temperature is too low. Ovens arenotoriously unreliable in their temperature settings。Use an oven thermometer and get your oven calibrated if need be. If your oven temperature is too low, then the fat will melt slowly just as described above before starches can set. If it goes quickly, then rising happens, starches set, and all of that.

最后，尽管这不太可能问题，但如果您使用的是发酵粉，那可能是超越它的素数。不要让您的发酵粉一年又一年坐着。它会吸收水分，在罐子中激活，并失去其所有上升能力。