Change the Way You Bake

Why Are My Cookies Flat?

Rigorous tests—all in the name of science.

December 19, 2019
Photo by BY ROCKY LUTEN

Are you one of those bakers that always remembers to soften butter before baking? To space cookies on sheet pans just as the recipe instructs? Or, chills cookie dough for the full requisite 2 hours—or, gasp, overnight? Well, I'm not one of those bakers.

In an effort to make as many cookies as possible, in as few batches as possible, with a limited number of baking sheets, I confess that I almost never give my cut-outs or balls the room they need. (What? Baking sheet real estate does notcomes cheap!) The result is almost always conjoined cookies, semi-circular once uncoupled (if uncoupled at all). Their misshapen looks a lasting reminder of my lack of patience and spatial awareness.

I spy some kissing cookies. Photo by James Ransom

But before I go rearranging my cookie baking placement, buying sheet pans I don't need, or start proactively planning (gasp!) for softened butter needs, I think the question that needs answering most is: why do cookies spread, and how much power does a baker have, working within the confines of one recipe, to reduce that spreading? I did a few tests to figure things out—but first, the why of the matter.

My (highly scientific) cookie-spreading tests.

What's the deal? Why do cookies spread?

There are several reasons why cookies lose their s#!t flop out, according to David Lebovitz, Deb Perelman, Dorie Greenspan, and others.

  1. Greased cookie sheets promote spreading. Giving your cookies something with friction to cling onto, so to speak—like an ungreased baking sheet or one lined with parchment or Silpat—can slow the spreading. A greased sheet just encourages hot, melting cookie dough to run further.
  2. Butter that's too cold. When a recipe calls for room temperature butter, you should be able to make a small indentation easily with your finger. If the butter is too cold and hard, you'll have to mix the cookie dough longer to get it to properly incorporate, which can lead to...
  3. Dough that's too airy. As Dorie Greenspan explains in Dorie's Cookies, it's important not to take the first step of many cookie recipes—beating together the butter and the sugar—too far. The goal, usually, is to only incorporate the two ingredients without reaching the "light and fluffy" stage. When you mix the butter and sugar together at high speed or for too long, you'll aerate the dough excessively, causing the cookies to rise—and then fall—in the oven.
  4. Dough that's too warm. Chilling solidifies the fat in the dough, which means that the cookies will melt slower under the heat of the oven. This results in taller, thicker cookies better at holding their original, formed shape. You'll see that, even when a recipe doesn't explicitly require it, many bakers recommend chilling cookie dough thoroughly—for at least two hours in the fridge— to slow spreading and to make the dough easier to work it (as in the case of cut-out or slice-and-bake cookies).
  5. A wacky ratio of sugar, butter, and fat. Too much sugar, too much butter, or too little flour can all contribute to cookies that are on the run. (In the case of cookies that spread no matter how careful you are preparing the dough and/or the baking sheets, I'd probably turn to another recipe.)

What Can I Do About It?

I decided to futz with drbabs's Magical Marvelous Memorable Cookies to see if a few simple factors—chill time, oven temperature, and lining a cookie sheet—could really make a difference. I chose this specific recipe, one, because these cookies are known to spread (drbabs says so) and, two, because every time we've made them at the Food52 offices, they've turned out a little different. Just take a look at how much puffier the cookies on the right (which were made more recently) are than those in the original batch:

The old photo (left) versus the newer photo (right). Photo by James Ransom, Rocky Luten

How would changing some simple variables affect how (and how much) the cookies spread (keeping in mind, of course, that each ball would sprawl slightly differently depending on the concentration and distribution of M&Ms, granola, pretzels)? I split one batch of cookies in four and baked each a little differently:

  1. Baked at 375°F immediately after the dough was mixed, against the recipe's instructions.
  2. Frozen for 20 minutes, then baked at 375°F, as the recipe recommends as an option.
  3. Refrigerated for 1 hour, then baked at 375°F, as the recipe recommends as an option.
  4. Refrigerated for 1 hour, then baked at 300°F, per a tip on King Arthur Flour's website that suggests stymieing spreading by baking the cookies at a lower temperature for a longer period of time. At a lower temperature, the cookies are able to set before the fat melts, their theory goes.

Using the June Oven, a super high-tech smart oven that has a camera inside of it, peering down on the food (it can detect when you've put in broccoli versus salmon versus brownies versus delightfully-chunky but problematic cookies), I was able to watch the cookies as they spread—and to automatically record each batch in a video saved to my phone (and then geek out over this bird's eye view I'd never seen before!).

From puffiest (top left) to flattest (bottom right).

Here's what I saw (and found, and tasted):

Cookies Baked Right Away

The cookies I baked immediately, without chilling at all, spread the most—though their movement was not detrimental to taste or appearance. This confirmed what drbabs warned against in his recipe, and why he called for a rest in the fridge or freezer. Fat in a dough not permitted to chill or solidify will encourage the dough to spread more readily.

A little less flat, these were still the cookies that most resembled the first batch we made at the Food52 offices (the photo on the left of the diptych above). That made me wonder: Perhaps I had creamed the butter and sugar less vigorously than had the original test kitchen baker, or was heavy-handed when measuring the flour. Or, maybe that same test kitchen baker had too not been a cookie angel, and baked that first batch without chilling the dough at all. Regardless of the reason, these cookies definitely emerged the thinnest and flattest of my four tests.

Even a 20-minute stint in the freezer makes for a cookie with less sprawl.

Cookies Baked After Chilling

The cookies that baked after 20 minutes in the freezer were the second flattest, noticeably thinner than those that spent an hour in the fridge. I had expected that the dough balls, frozen only for 20 minutes, would have spread less than the ones that had been refrigerated for an hour—but the dough must have not gotten quite as cold. More than degree of chill, time spent chilling seems to have had the largest impact on cookie spread. Had I frozen the dough for an hour, rather than just 20 minutes, might that have changed? It's likely. Regardless, both chilled batches spread less dramatically in the oven: Even 20 minutes has an impact.

Cookies baked after 20 minutes in the freezer (they hold their ball shape for a while, then spread rapidly):

Cookies baked after 1 hour in the fridge (they spread more consistently throughout the duration of the cook time):

Cookies Baked at a Lower Temperature After Chilling

The cookies that looked the most different from the rest were those baked according to King Arthur Flour's tip to bake at a lower temperature (at 300° F, as opposed to 375° F), and for much longer (25 minutes as opposed to 14).

This batch emerged blonde all over, with no thin, crispy circumferences. The lower the temperature, J. Kenji López-Alt of Serious Eats explains, "the more evenly the cookie bakes, with less of a contrast between the edges and the center." At the lower temperature, the cookies effectively slowly dry out and set.

Chilled dough + a cooler oven = a paler, puffier cookie.

Many cookie experts warn against a too-low oven temperature (David Lebovitz writes that it "can prolong the time it takes for cookies to bake, giving them too much of a head-start in the race against spreading"). But I found that the batch cooked at a lower temp held their shape best. So, it depends what kind of final texture and look you want: sometimes, a uniformly-textured, not-too-browned cookie cooked low and slow is what you want (like with shortbread). But other times (really, most times), the contrast between the crisp edges and ooey-gooey centers, that comes with baking for a relatively short time at a high heat, is what you're after (like these).

But, of course, it's ultimately the temperature of the dough that had the largest impact: Had the dough itself not been cold from the fridge when it went into the lower-temperature oven, the results surely would've been different.


And in the end, all the cookies were crunchy and crispy. While those that I baked at 300°F had a little more heft and chew in the middle, they were still brittle—they snapped in half with a hard crack, just like the batches baked at 375°F. Ultimately, the nature of the cookie did not change, no matter the chill time or oven temperature.

For kicks, I also tested parchment paper versus Silpat, putting both sheets in the same oven for the exact same period of time, rotating halfway through. The cookies on the Silpat-lined sheet did spread slightly more, but their bottoms were lighter. This is perhaps because of the nonstick, slippery coating on Silpat sheets, that, if you remember from above, encourage spreading. The parchment paper provided only slightly more friction to the cookies.

The parchment paper cookies held their shapes better (but only slightly).
The cookies baked on parchment (left) were darker than those baked on Silpat (right): It's most evident in the M&M bottoms.

If, after all of this, you still find yourself with dough that spreads too much, Food52er butter-sugar-flowers has a wonderful suggestion: Drop the balls into a muffin tin (or a mini muffin tin) before baking. Uniform size, uniform thickness, and no risk of pancaked cookies. Another option is to scoop dough balls with a cookie scoop onto a baking sheet, freeze the sheet until the dough balls are thoroughly hardened, and bake straight from the freezer. Cold dough balls going into a hot oven will spread slower than room temperature, unrested dough balls.

Or seek out a cookie you know will be dense, thick, and chewy:

Or one destined to be very thin and crispy:

You could also embrace cookies that spread. Make a skillet cookie, or even better—One Big Cookie. Deliberately under-bake the first, not only allowing but admiring the way the cookie, warm and melty, runs onto your spoon. Let Dorie's vast cookie monopolize your baking sheet real-estate. Break it into organic, sculptural shards, and munch while you wonder why anyone ever cared about perfectly round puffies anyway.

Try a few tester batches yourself!

Determined to make drbabs's challenging cookie work? Experiment with chilling temperature and duration, cookie-scooping and freezing the dough, or baking at a lower temperature. Let us know what you find in your (delicious) tests.


Do you prefer cookies that are tall and domed or flat and squashed? And what steps do you take to get your cookies to cooperate? Tell us in the comments!

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Sarah Jampel

Written by: Sarah Jampel

A (former) student of English, a lover of raisins, a user of comma splices. My spirit animal is an eggplant. I'm probably the person who picked all of the cookie dough out of the cookie dough ice cream. For that, I'm sorry.

24 Comments

Jess L. April 6, 2020
Hi, I have tried many things so far- like chilling in the freezer for 90minutes in the ball shapes.
Also tried different temperatures and they still spread....
in my recipe I used plain flour, not self raising. Adding extra tablespoon of self raising flour would make the difference or not?
 
Matt H. December 30, 2019
I noticed you measured your ingredients by volume. When you use volume to make your cookies, every batch will be different so your conclusions are not really that valid. It would be great to see if your outcome is still the same by using the exact same quantity of ingredients by weight and to provide the recipe by both volume and weight.
 
Christine November 18, 2018
No scientific advice, but I use a cookie scoop. Flatten the dough in the scoop against the side of the mixing bowl. Takes a little longer, per batch, but cookies all bake to a consistent size. And they all fit perfectly into the muffin liners used in my Christmas Cookie tins. I bake 10 different types of cookies (last year's total was close to 1,200), and haven't had a complaint yet about consistency or taste!
 
mrslarkin November 18, 2018
Oh my goodness! 1200? That is impressive!
 
Christine November 19, 2018
And exhausting ... but worth it! Four dozen cookies per tin. No Christmas shopping for us. We give cookies!
 
mrslarkin November 19, 2018
Now I need to know what types of cookies you make! I’m starting my Christmas cookies next week!
 
Nana June 12, 2018
Thank you for all the comments as I will try a few. One of my problems is that I moved from a low and dry city to 8300 feet altitude. Sure made a difference in my baking and some of my cooking.
 
Margaret M. January 17, 2017
The blue tape made the labels in the photos completely unreadable.
 
Author Comment
Sarah J. January 17, 2017
Yes, sorry about that! I wrote explanations in the captions, so I hope that helps!
 
Henry J. January 16, 2017
Sarah,
You are a food scientist!!
 
dianne January 15, 2017
Hi!
I have found putting in 1/2 butter and 1/2 shortening stops the spread in my chocolate chip cookies. That's the only thing special I do.
 
Cate January 13, 2017
I've found that subbing a quarter or so of the flour with whole wheat pastry flour helps cookies keep their shape. No chilling, and I partially melt the butter to make the dough.
 
Danielle W. January 12, 2017
my drop cookies never spread, my spritz cookies however, need a couple of test batches before I get the dough right. what's that about?
 
mrslarkin January 12, 2017
Thanks for your research, Sarah! For me, I have found the temperature of the butter prior to adding to the dough has the biggest effect on the outcome of the cookie. Very warm room temp butter will make the cookie spread like crazy. And freezing the dough after won't make much of a difference because the warm butter has been mixed into the flour already. Also, I have found baking soda makes cookies spread, so increase or reduce in a recipe depending on what you want to make happen.
 
Smaug January 12, 2017
I suppose all this stuff makes SOME difference, though it seems most of it would be negated by checking the cookies rather than baking strictly by time. I must say that I usually bake cookies as soon as the dough is made, that I generally start with cold butter, and that I almost never have a problem with running. Cookies that require three sheets don't show any noticeable difference despite the fact that the third sheet has been sitting at room temp. for a considerable period before baking- they're sometimes a shade faster, but nothing significant, and I think that has more to do with the oven than the dough. One tip- drop cookies are less likely to run if made into neat balls with damp hands (most of them should be flattened afterward)- they will be more uniform, but you may miss the extra crisp edges.
 
PieceOfLayerCake January 12, 2017
Its really just about creating a proper emulsion between the butter, sugar and egg. That is done by adding ingredients that are the proper temperature to each other slow enough to allow the emulsion to catch. That's a cornerstone of baking anything that has a high fat content.

Another thing so many recipes fail to mention is the importance of scraping the sides and bottom of the mixing bowl....especially when using a stand mixer. If you have pockets of fat or sugar in your batter that hasn't been properly incorporated it will erupt out of the dough in the oven causing spread.

Also, you have to be careful not to over beat the eggs. If you incorporate too much air in the egg phase of the recipe, the cookie will souffle and collapse into a flat, craggy mess.
 
Smaug January 13, 2017
The wore "emulsion" refers to a relationship between (unlike)liquids.
 
PieceOfLayerCake January 14, 2017
Exactly, like when you add the LIQUID egg whites into the batter, it has to emulsify properly with the fat in the butter....that's why you don't just dump it all in at once. I know what I'm talking about, you don't have to school me on vocabulary.
 
Smaug January 14, 2017
Mr. Webster would disagree- hardly a colloidal suspension, but OK.
 
PieceOfLayerCake January 18, 2017
Dictionaries aren't culinary experts...are you arguing with me on the definition of a word or the function of a recipe because I'm pretty sure "Mr. Webster" has his own website. If you disagree on how I explained the chemistry, by all means, tell me how I was wrong.
 
Smaug January 18, 2017
Look it up anywhere you want- what you're talking about is not an emulsion. You run, for one thing , into the problem that you only have two liquids- egg white and yolk ( which can,, indeed, be emulsified with each other but aren't in this procedure. You add the eggs one at a time because otherwise you get lumps of solid more or less floating, and they are very difficult to combine for purely physical reasons- like trying to stir dirt clods into a bowl of oil. An emulsion is a suspension of droplets of one sort of liquid in a continuous bath of a different liquid- like a vinaigrette. The sugar/flour/ egg mixture that cookies start with is just a mixture- many people do it with a wooden spoon. From a culinary standpoint, your post really amounts to saying that the ingredients must be mixed properly, which is certainly true- if you have pockets where the fat content is excessively high- like the stuff that wants to stick to the bowl- your cookies will likely run.
 
PieceOfLayerCake January 18, 2017
Again....so what I said was true but you're STILL just arguing about the use of the word "emulsion". Thank you for rewording what I already typed...go troll someone else.
 
Smaug January 19, 2017
Since you're resulting to gratuitous insults, may we assume that you're conceding the point? Sure, your post was essentially correct (not to say that's THE problem, but it is A problem) despite stretching what required a simple sentence into a page of pseudsoscientific babble.
 
Rita January 22, 2018
Is it really necessary to argue, over such a small thing, Why not have a friendly discussion over the differences of a mixture, emulsions, etc.