Two cookies made from the same recipe app/Photo by Donna Turner Ruhlman

Last week I asked what makes a great app?  Andrew Schloss, a cook, teacher and author of numerous books, offers his answer below. Andrew has created a truly innovative cooking app, called Cookulus.  His plans are to create a series of interactive recipes that can be used by Cookulus but for now, he and his collaborators have started smart and small, applying the Cookulus algorithm to the chocolate chip cookie.

I recommend this app even if you don’t actually bake a cookie from it, just for the fascination of watching the recipe adjust itself as you slide your fingers along the bars (I bought it for $2.99, but he and his collaborator, Max Minkoff, reduced the price to a ridiculous $.99; they also offer a “lite” version for free to give you a better sense of the app). If you do cook from it, know this: it works.  See photo above. Innovative and truly unique. Here’s Andrew on it’s genesis.


Teaching a Recipe To Think For Itself

by Andrew Schloss

I have been a cookbook writer for 20 years, and I have been making cookies for more than 50, but I don’t think I really understood what I was doing until I had to teach an algorithm how to bake a batch of chocolate chips.

About a year ago, when the iPad was announced, my friend Max Minkoff and his app development partner Bruce Zenel got psyched by its possibilities in the kitchen.  Max came over to see if he could hook me in to working on a cooking app.  There were already several dozen out there, but no machine that made it easy to use electronic recipes without printing them out.  I’m a cookbook writer who’s geekily attached to the intricacies of recipes, so while Max and Bruce were panting at iPad’s interface possibilities, I just wanted to rewrite the book on recipe writing.

The restrictive thing about writing recipes is that unless home cooks have a lot of cooking knowledge to manipulate what’s on the written page they are stuck with what I write.  But on a tablet or smart phone (or anything with a touch screen) the user should be able to change what is happening in the recipe at will.  Through sliders or pull downs these machines could allow anybody to interact with a recipe the way that I do, altering it to make exactly what they want to eat.  All I had to do was write a recipe that knew how to think, and to do that all I had to do was teach an algorithm how to cook. This was going to be fun.

Algorithms (basically a list of instructions that calculate a function) are linear and relentless. They can only calculate a single set of actions but they do it without a hitch until you force them to stop.  The possibilities of cooking with one were decidedly cool and potentially expansive to a nonlinear mathematically-challenged thinker like me.  Initially I was convinced it couldn’t possibly work. Baking was too idiosyncratic.  Ratios worked in general, but they couldn’t be relied on to make something delicious every time without significant tweaking.  Max listened to my rant patiently and then he brought up the game changer, “Wouldn’t you rather try to create an elegant mathematical solution?” Not being one to turn my back on elegance I acquiesced and we decided to start with something manageable and small, like a chocolate chip cookie.

The first thing was to decide what decisions we wanted the algorithm to make.  With cookies that was fairly simple.  Other than flavoring and what kind of chips, there is a defined set of criteria that differentiate one chocolate chip cookie from another:

1. How thick or thin?

2. How soft or crispy?

3. How chewy or crumbly?

And a set number of ingredients that influence those criteria: fat, sugar, flour and egg, plus two baking factors that play against one another: oven temperature and baking time.

Here’s how it works: if you want to make a cookie crisper you increase the ratios of sugar, flour, and butter to egg, you increase baking time and decrease the oven temperature.  Thicker?  Go for more flour, less butter, hotter temp, and shorter baking time. Chewier? Lower everything against the proportion of egg.  Here’s a table that lays it all out:

Useful info but fraught with pitfalls. Too much butter (especially when teamed with a reduction in flour) and the cookie could disintegrate into mulch. Overdo the brown sugar and your cookie will never get crisp; too much white sugar and you’re stuck with shrapnel. In order to put all this knowledge to work we needed a base recipe so resilient and sure footed that no amount of manipulation would make it crumble.

I have never been a fan of mean recipes (those averaged from a group of recipes, not recipes with a grudge). Modified by mathematics and polished to remove any perceivable personality, they are formulas without authorship. But what they lack in soul they make up for in strength.

We collected more than two dozen chocolate chip cookie recipes from cookbooks, websites, and package backs, and laid them out on a spreadsheet, lining up the ingredients, tossing outliers, and standardizing measurement.  We decided that regardless how the ratios of ingredients came out the resulting recipes could only call for whole eggs – no fractions.  This meant that a large egg (52 grams) became our unit of measure.

With everything standardized and some simple arithmetic (add all the flour and divide by 27), we got our mean.  I had to make a batch right away, and within 30 minutes we had two dozen perfectly delicious undistinguished cookies – exactly what we wanted – neither thick nor thin, soft nor crisp, chewy nor crumbly.

I can’t tell you the exact algorithm that turned that single bland base cookie recipe into 1500 truly unique variations (Max and Bruce would fillet me), but I can tell you that it worked without a hitch.  I was floored.  Everything I tested came out as the algorithm predicted, until a day about 6 weeks in when everything threatened to blow up.

I had dialed a formula into the system that was ultimately thin, ultimately crisp, and moderately chewy.  I had already mixed up the batter before I noticed the baking time and temp – 45 minutes at 260 degrees F.  (What the?) No cookie bakes for 3/4 of an hour.  But I already had the cookies on the sheet pan so I stuck them in the oven and called Max to try to figure out what went wrong with the algorithm.  Forty-five minutes later the cookies emerged buttery crisp, tuile-thin, with the barest hint of chew. “(Expletive!), the thing worked.”  Not only did it work, but in it’s own relentlessly single-minded algorithmic way it had figured out a formula for the ultimate crisp thin cookie that in 40 years of professional culinary experience I had never come across. Completely awesome!

Turning all of this into an app, coming up with a name (we settled on Cookulus—for it’s similarity to calculus—after Cookini got taken), designing graphics and an interface, and going through the months of debugging that turn a cool idea into something useful and salable is another story, but in the meantime Cookulus is up and running—the first interactive recipe out there. I’ve had my butt kicked by an algorithm and I’m a better cook for it.

If you liked this post on Cookulus, check out these other links:

© 2011 Michael Ruhlman. Photo © 2011 Donna Turner-Ruhlman. All rights reserved





19 Wonderful responses to “Cookulus”

  • David Dadekian

    There’s a phenomenal Good Eats episode based around this concept that I’ve relied on for years of cookie making. It sounds like Cookulus takes the thin, chewy, crispy thing to a whole ‘nother level. Wow. I’ve got to have it. Hope it’s on iPad. Would love for my Droid phone too.

  • ruhlman

    It’s available for iphone and ipad. not android devices.

    • JB in San Diego

      I was excited about this and rushed to buy it, but unfortunately it requires the iPhone 4.2 iOS upgrade, which isn’t compatible with my 1st generation iPod Touch (3rd & 4th only). I wish app developers would consider us non-early (late?) adopters when they write apps – especially something like this which I’m sure doesn’t need the horsepower of the latest hardware.

      • Max

        We’re touched that so many folks are interested in what we’re doing!

        The iOS 4 requirement was something we did indeed consider, but there are some changes between iOS 3 and iOS 4 that make it more complicated to support both. But more to the point, yes, in fact earlier hardware does have a hard time running Cookulus effectively. We’ll try to take another look though!

  • Chef Philip Geneman

    That app sounds so useful. I love to bake cooking sometimes ( I do better with cooking than backing) in culinary school I began to like baking better than I used to because of a great internship that included bake shop in the Adam’s mark hotel in Denver. I learnd a lot about baking cookies and other treats. I wish I could get it I have an android.

    Thanks 🙂

  • jbl

    Hallelujah! Exactly that for which I was waiting. Also for me a personal triumph of sorts since I am always the one arguing in favor of mathematics (ultimately) to solve problems for which people imbue with joking mysticism or dismiss with non-quantitative terms (“the baking gods”, “with a bit of luck”, “you develop a feel for it”, etc..).

    The algorithm(s) shouldn’t be too hard to reverse engineer (and tweak) for an Android app now that a “proof of concept” exists.

    Great post!

  • Natalie Sztern

    I bought it for both my iphone and ipad and it is COOL…especially for me – for whom conversion, weights and measures and anything else that requires math is an impossible task. I would love a smaller yield (24 is too much for my house) and if I had a wish list… how to take these recipes and batch the dry ingredients to have on the shelf for when I am in the mood to make a few cookies and then how much of the liquid I should use to stir in and drop by teaspoon onto a baking sheet….

    • Max

      We’d love to have smaller yields but the egg is the limiting factor. One egg makes (roughly) 24 cookies. Fractional eggs seemed impractical and confusing.

      This was part of Andy’s motivation for writing a blog post about Ten Things to Do with Stale Cookies:

    • Carol

      You can make the dough, then divide it into portions that fit your household, then freeze the rest. Cookies for now, cookies for later. And, bonus: The dough seems to improve from the freezing process. In fact, when I make chocolate chip cookies, I shape the dough, then freeze it all, and bake up what I need as I go.

  • Mark

    Simply amazing. I was a math major in college and I cook. Why didn’t I come up with this! Love this App.

  • PJ

    Love the app idea, loath the interface. They could really use a better design ethic. The best and most popular iOS apps stem from a great idea executed with elegant design

  • cheap customized jerseys

    I love to bake cooking sometimes ( I do better with cooking than backing) in culinary school I began to like baking better than I used to because of a great internship that included bake shop in the Adam’s mark hotel in Denver. I learnd a lot about baking cookies and other treats. I wish I could get it I have an android.


  • Wilma de Soto

    Cookies are one of the most demanding things one can bake yet seem so simple. The difference between a good cookie and a great cookie matters not what’s in the dough. It’s knowing your oven, turning the cookie sheets and minding them vigiilently until you see what doneness you want. It’s a royal pain, but worth every bite.

    Deal with it.

  • Berto

    Just wanted to say that I bought the app on a whim for my Ipad and it is the bees knees. I’ve made a few different types of cookies and they came out exactly like they should have each time ( one batch was used to make ice cream sandwiches!). I’ve been telling folks how great cookulus is and I look forward to more recipes.

  • Jeff

    I made my first batch tonite. Exactly to my wife’s Perfect Cookie specs….amazing! I am with Michael, I can foresee the day that we will have apps like this for many more recipes. Next up is a little more crispy and thinner for me!

  • Bethany

    LOVE the app idea and tried your “chocolate chip cookie bowl” recipe as cookies. They came out crispy, which was great, but incredibly flat. Plan to go back to my own recipe, but will use your ratio chart. Thanks!


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