The Great Cookie Experiment

Have you ever wondered why cookies sometimes turn out flat? Too puffy? Why they are overly brown on the bottom but still gooey inside? What type of pan or liner you should use? Or am I the only one that obsesses about such things?

In the event that there is at least one of you out there who ponders these deep questions, I decided to undertake The Great Cookie Experiment. First up was testing butter temperatures since this may be one of the most critical pieces of cookie baking. In fact, I posted on The Facebook a week or so ago that I spent the entire morning making a bazillion batches of chocolate chip cookies to test out certain theories and that in the end, they all looked the same! Well, I am here to report that I need to withdraw that claim because upon closer inspection, I found that butter temperature did, actually, make a pretty significant difference in cookie outcome.

And I’m here to share the results with you. Stay tuned over the next few weeks as I get to the bottom of more scientific and totally important cookie conundrums (feel free to inquire about certain cookie problems in the comments and I’ll add them to my to-test list!).

First of all, for the following scientific report, there are a few givens:

1) We are using a recipe that calls for room temperature or softened butter. Even though some cookie recipes call for melted butter (in fact, my personal favorite chocolate chip cookie recipe calls for melted butter), those recipes are void for these test results because they have been created based on melted butter as the base. My test was run for cookies calling for softened butter, which most do.

2) We are using the scoop and sweep flour method. The way flour is measured can significantly impact results! Read more about that fascinating topic here.

3) We are using a basic chocolate chip cookie recipe that I’ll provide at the end of this post.

4) Throughout this post, I’ll be using very technical terms for the butter temperature as follows:

Cool Room Temperature Butter: means you can push your finger gently into the butter to make an indentation but it’s not so soft that your finger easily slides through the entire stick. Make Sense?

Way Too Soft Butter: means your butter is, um, way too soft. It might even have tiny melty spots if you tried to soften too aggressively in the microwave (ahem, which I never do, right!). Your finger will easily slide through the stick of very mushy butter.

Melted Butter: means your butter is melted. Wow. These are difficult concepts, I know.

You can see in the picture below how the cookie batters already look quite different. This is right after the eggs and vanilla have been added and beaten into the batter. Please forgive the different bowl size. My life has only so many Pyrex bowls.
The Great Cookie Experiment

Now behold a bird’s eye view of the batter after the dry ingredients and chocolate chips have been added. Pretty easy to tell how the batters are different based on the butter, right?The Great Cookie Experiment

After the cookies are baked, the differences are pretty obvious (even though I failed to recognize them in my hasty FB post of yesterweek). The first cookie with cool room temperature butter is picture perfect. It baked evenly and held it’s shape, flattening beautifully without overspreading. The way too soft butter cookie doesn’t look too shabby but if you look closely, you’ll notice that it’s a bit doughier and slightly greasier than the cool room temp butter cookie, although it still held it’s shape pretty well. The melted butter cookie? Misshapen and just not up to par with the others in looks. In taste it wasn’t too far off, but like the way too soft butter cookie, it was greasier in texture and too underdone in the center even though the edges and bottom were browned (and just so you know, I eat all cookies equally so no cookies were harmed or thrown away due to superficial imperfections).
The Great Cookie Experiment

Here’s an up close and personal look at the melted butter cookie. Hardly round, and while you can’t see it, much flatter than the other cookies. Oh, and please disregard my chipped mini platter. Totally not worth photoshopping out. It’s kind of a peek into my real life: chipped platters, misshapen cookies and all. Welcome to my world!
The Great Cookie Experiment

The way too soft butter cookie…pretty good except for the underdone middle and slightly greasy taste/texture.The Great Cookie Experiment

And finally, the star. Cool, room temperature butter produced the prettiest cookie with the very best texture.The Great Cookie Experiment

So there you have it: the results of the 1st installment of The Great Cookie Experiment! I’ll be bringing you other details soon like what to line the pans with (parchment, silpat or lightly greased) along with a few other good tips. In the meantime, here’s the cookie recipe I used and again, feel free to leave any questions/feedback in the comments!

Happy Cookie Baking!

Basic Chocolate Chip Cookie Recipe {For The Great Cookie Experiment}


  • 1 cup butter, cool room temperature
  • 1 cup granulated sugar
  • 1 cup packed light brown sugar
  • 3 large eggs
  • 1 teaspoon salt
  • 1 teaspoon vanilla
  • 1 1/2 teaspoons baking soda
  • 3 1/2 cups flour
  • 2 cups chocolate chips


  1. Preheat oven to 350 degrees. Cream butter and both sugars together until well mixed. Add eggs and mix for 2-3 minutes, until the batter is light in color. Add salt, vanilla, baking soda and mix. Add flour and chocolate chips together and mix until combined.
  2. Drop cookie batter by rounded tablespoon onto parchment paper or silpat lined baking sheets and bake for 10-12 minutes until lightly golden around edges but still soft in the center.

Recipe Source: adapted from this recipe

138 Responses to The Great Cookie Experiment: Butter Temperature

  1. Taylor says:

    Hi Mel!
    I tried this experiment myself for a science project, yet, every batch turned out the same. Every batch came out with cookies that were round, full and had held there shape. I followed your recipe, so I am very curious as to what would have caused these strange results. Did you microwave your butter? & would stirring in ingredients by hand change the outcomes? I am looking forward to hearing back from you:)

    • Mel says:

      Hi Taylor – hmmm, that’s kind of strange! Although the differences are subtle, they should be apparent (like shown in the pictures in this post). I’m not sure if stirring ingredients by hand would make a difference but it very well could, I suppose, since a mixer incorporates at a totally different speed. I did microwave my butter. Did you?

  2. Taylor says:

    Hi Mel!
    I agree this sure is strange! It sure has kept my mind busy, trying to think of possibly variables that could have cause each batch to turn out the same. I didn’t microwave my butter, instead I heated it up in a sauce pan (not too sure if this would cause much change). I also didn’t grease, or line my baking sheet with parchment paper. Instead I just rolled my cookie dough into balls by hand, and placed them on the plain baking sheet. In your opinion do you think not greasing or lining your baking sheet would make a significant difference. Or possibly could the reason be that I rolled the cookie dough into balls by hand?

  3. Julie says:

    It was a mystery until you said you rolled the cookie dough into balls. Any handling of dough affects the dough itself, and this would have had a big effect, overruling any of the subtleties of the butter.

    • Nikki says:

      Ohhh, I was also rolling the cookie dough and the cookies came out different than ever before. I’m going to try dropping them on the pan next time like you suggested below. Thanks for the tip! πŸ™‚

  4. Taylor says:

    Really? I had no idea that handling the dough by hand could affect a cookies outcome. Knowing this really explains allot. Do you have any idea why this would have such an impact? I am really interested in find out.

  5. Julie says:

    It’s the same reason you handle pie dough as little as possible. Mel the Great will know more. I’m sure she’s a scientist when it comes to food, but the more we handle dough with wheat flour, the more the gluten has an effect. I won’t mix cookie dough with a mixer for this reason — I do it by hand. Rolling the dough, even that small amount, affects the wheat and the butter. At least, that’s been my experience. I loved this experiment Mel did with the butter and my practical experience over the years has been the same.

    • Mel says:

      Hi Taylor (and Julie!) – I think Julie might be on to something with the rolling of the dough, although I have to admit that when I spoon out my tablespoon-sized balls of dough with my cookie scoop, I usually give them a quick (as in 1-2 seconds) roll in my hands to make them perfectly round (I did that with this experiment) so I think for the dough to be really affected, you’d have to be scooping it out of the bowl with your hands and rolling it for much longer than I do – all of which will feed some of your body warmth into the cookie dough and like Julie said, that can affect butter temperature, etc. If it’s just a quick roll, I’m not sure it would be the only factor for your results. The only real way to test, though, would be if you made another batch exactly the same but didn’t roll the dough balls by hand (used a cookie scoop of two spoons) and compare the results.

  6. Taylor says:

    Hi Mel!
    I will admit, when I was rolling the cookie dough into balls it wasn’t a quick one second roll. Since I was doing this experiment for a science project, I wanted each of the batches to start off with cookie dough balls the exact same size, so I thought rolling them into perfect balls similar in diameter would help control the variables. I am going to duplicate this experiment but this time I will not roll the dough into balls by hand. Hopefully this time I get some conclusive results. πŸ™‚

  7. Julie says:

    The dough will shape itself into a nice cookie without any handling on your part. Just get the lump onto the baking sheet. I hope your experiment turns out better this time. What an experiment!

    • Lorna says:

      I just did this with my daughter. Like Taylor all our cookies came out about the same! We just dropped them onto the cookie sheet with a scoop. The doughs did look different in stickiness, but cooked they all held their shapes and looked the same! Very interesting. My daughter was a little bumbed that there wasn’t a difference like we thought, however, they are all very tasty! We made them for our family reunion. I have always wondered if the butter temp really mattered. We might try again, but with a different recipe, or maybe not!

  8. Christine says:

    Hello~ Mel:
    I have been being so curious about this for a long time.
    Thx for your experiment.
    But I wanna know more about how they taste!
    Thanks :))

  9. carool says:

    please, the cookie with cool romm butter becomes soft in the middle? i like cookies soft.

  10. James says:

    This was amazing. Thank you.

  11. Marlene says:

    I am so glad I came across your website! I was making squares with a shortbread crust & was trying to warm the butter in the oven. I got distracted & the butter melted. I added the other ingredients & it turned into a goopy dough. I googled salvaging a crust & came across your test results with the cookies done with butter 3 ways. I decided to take a chance & go ahead with the “crust” the way it was. I poured it into a pan, refrigerated it, then baked it & the squares turned out just perfectly !

  12. Baagasgs says:

    Just real quick

    Great effort on this, I just found this while searching what I thought was going to be a fruitless google search

    Nice website

  13. Chris says:

    Can you or anyone on here explain “WHY” the cookies come out differently? My 9yr old is doing this for her science fair and I’m/we are having a hard time finding out “WHY” they come out differently. We just don’t understand it.

    • Andria says:

      Chris –

      There was a New York Times article several years ago detailing the “WHY” of this. (It was a lengthy article, so it may have been in their magazine section.) I remember the article talking about the science of it. Something happens to butter at 86 degrees. It undergoes chemical change of some sort. (Chemical rather than physical because if you get it colder again it’s not the same at the molecular level. And anyone who has done this knows it’s just not the same…)
      Also, when working with cookies, the first step is to cream the butter and the sugar. When you do this, the sugar breaks down the butter in a way that leads it to be fluffier when butter is colder. It gives it tiny little “air bubbles” which made your cookie puffier rather than a thin cookie with melted butter.
      I’m not a scientist so I hope that all made sense. I would try and look up the NY Times article. It was a fascinating read and would probably answer most of your questions.

  14. Taylor says:


    I found this video very helpful and approachable when I too was trying to determine “WHY”.
    Check it out!:

  15. Chris says:

    Thank you so much!! This is very helpful. I’ll spend some time looking for the New York Times article and she’ll love a video to watch. Thank you. I’ll let you know how the science fair goes…

  16. Karen says:

    Thank you for taking the time to provide this valuable cookie baking information. Now I know why my dough is just not right. I microwaved the butter! I’ve written down the most important parts of your information on a piece of paper and will tape it in my cupboard for future reference.

  17. Bethany says:

    My son is doing a science project about states of butter and how they affect cookies. I am baffled by our results. I totally expected the melted butter to give a flatter cookie, however, the chilled butter (straight from the fridge) yielded the flattest cookie. I have read about the science behind cookies and I can’t figure out why this happened!

  18. j says:

    will chilling the cookie dough before baking change anything related to diff temps of butter? i always chill the trays for 10 min bef baking.. so they wont spread too much.

  19. Rachel says:

    So, my question is: what is the best way to soften butter? Often times I have used a microwave at very short intervals, constantly checking to make sure it didn’t melt too quickly. However, we no longer own a microwave. Sometimes you just can’t wait several hours for butter to soften at room temperature! Any suggestions?

    • Mel says:

      I saw a good tip somewhere the other day to put the wrapped stick of butter in a bowl of warm water. Since butter is a fat – any droplets of water inside should roll right off.

  20. Fernando says:

    That’s exactly what I was looking for!
    All recipes I find uses melted butter, and the results are usually the “melted butter” or sometimes, when I “got lucky”, the “way too soft butter” cookies.
    I was trying to figure out what I was doing wrong, because I could see it was something wrong in the early stages of the process.
    Gonna try again, now with the tips you provided.
    Thank you πŸ™‚

  21. j says:

    Why would the butter temperature affect why the cookies were undercooked in the middle?

  22. Cathy says:

    I tried baking a simple sugar cookie yesterday. Based on your experiment, my cookies shouldn’t have turned out flat, but they did (like really flat – even though butter was at the correct temperature). I tried rolling the dough and chilling overnight before baking and the cookies turned out nice and thick. Is it also possible that I didn’t have enough flour in my dough?

  23. Cathy says:

    Nevermind, kept reading through your posts and I think I found my issue πŸ˜› I’ll start measuring flour properly πŸ˜‰

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