A couple of weeks ago I received a rather unexpected but intriguing question: How do I bake a soft cookie at high altitudes?
This is a bit of a challenge to answer, as I can't exactly test the methods I read about at Memphis's average 331 feet above sea level. I can, however, give you an experienced baker's report of research on this question, as well as some pointers about baking a soft cookie if you live in Memphis at more standard altitudes!
So what's so great about a soft cookie anyway? I've heard reports from my mother and grandmother that the taste for soft cookies is a relatively modern thing. Decades ago the preference was for harder cookies that stored well in the cookie jar over the course of a week and held up to dunkings in milk, tea, and coffee. I don't know for sure, but I would speculate that (yucky) innovations in prepackaged foods such as mono- and diglycerides that keep Chips Ahoy and similar products soft have at least contributed to the new ideal of the soft cookie.
But that's not to say that a homemade (or Muddy's-made!) soft, chewy, melt-in-your-mouth cookie isn't to die for! So first, some general pointers about baking soft cookies at home, anywhere!
The number one rule for baking soft cookies is: UNDERBAKE! Or at least, bake less time than you baked the recipe that time they turned out hard.
Keeping in mind the old-school preference for harder cookies, especially with recipes that originated pre-1970, you want to bake those cookies less than the suggested time to make a softer cookie. If the bake time is stated to be 10-12 minutes, definitely try 10 first! Or better yet, check the cookies half way through (and rotate your tray if you find one side is getting done faster than the other), and get to know what your cookies really look like throughout the baking process. Note how different our half-done Honey Rosemary, Double Chocolate Sea Salt, Chocolate Chip, and Peanut Butter Cookies look!
Know that most cookies do NOT look done when they are done. Generally cookies will begin to get golden and lose most of their wet shininess. With most cookies, you don't want to bake until the interior shininess is gone. Can you see the glistening gooeyness inside this Double Chocolate Sea Salt Cookie straight from the oven? Mmm.
Your cookies will be very soft and pliable when they first come out of the oven, and they will continue to bake at least another minute or two while they are left on the baking sheet. Watch your cookies and you will see them harden a bit and grow to look more 'done.' Use a good supportive spatula to flip your cookies over and/or transfer them to a cooling rack as soon as they are hard enough to do so. This prevents the bottom of the cookie from continuing to harden further due to exposure to the hot pan.
Also I would suggest to everyone, if you do not have an oven thermometer, stop making up excuses and purchase one! Make sure your oven is not hotter than the recipe suggests. If you do not live at high altitudes, you may try baking those cookies a few degrees lower than the recipe suggests (high altitudites, you are generally advised to bake your cookies at higher temperatures: see below for details).
Underbaking is a surefire way to make your cookies softer, but keep in mind your intentions with your cookies. If you are serving them fairly quickly in your home on a platter, you can make your cookies as soft as you like! But should you need to stack them or ship them to your friends out of state, you are better off getting them firm enough to not break, bend, or stick to their neighbor. Remember, the soft cookie from the grocery store that travels so well does so because of yucky food additives, nothing that can be replicated in your home kitchen!
Now, what about high altitudes? The rules are a little different when you get a few thousand feet above sea level, where the air is drier and holds less oxygen. Not only do you need to do some underbaking when making cookies in such conditions, but you may need to change your recipe a bit as well.
Your underbaking techniques will change a bit at high altitudes. Don't even think about turning your oven temperature down! You will want to crank it up anywhere from 10-25 degrees higher than your recipe suggests (don't forget to use your oven thermometer to gauge that temperature accurately). This will allow the exterior of your cookie to crisp up quickly and form a protective shell around the moist interior before it has a chance to lose all of its liquid to evaporation.
As for changing your recipe, there are a number of standard adjustments suggested for baking at high altitudes. Everyone, no matter the sea level, should make sure they don't overbeat the dry ingredients, but when you are up in the mountains, you may want to start easing up on beating when you add your eggs.
Beating your eggs well at lower altitudes adds air bubbles and a little OOMPH to the cookies, but that is not necessary in the lower air pressure way up high. The lower air pressure allows the cookies to rise far more--and more quickly--which causes them to then collapse in on themselves. And we all know a collapsed cookie is not a soft cookie!
Some recommend adding a little extra flour to counteract this collapsing. Just one to four tablespoons should do it, depending on your altitude and the recipe.
Also to prevent too much expansion in your cookie too early, most experts say to try reducing your baking powder and baking soda amounts by at least 1 tsp. Baking soda can cause as much as 20% more expansion at high altitudes, so using the normal amount is without a doubt counterproductive!
But, perhaps more importantly in our quest for the softest cookie, many suggest adding extra liquid. If there is no liquid in your recipe, just add a little water. Start at two additional tablespoons of liquid for every cup of flour. The highest altitudes and driest of recipes may need as many as four tablespoons per cup of flour, so get ready to experiment!
And that's the name of the game, folks, be you at 300 or 7,000 feet! Experimentation! We have to do a ton of that at Muddy's Bake Shop to guarantee you a perfect cookie every time. You may find you like to crank your oven to 400 and bake your cookies just 5 minutes. Or maybe adding an additional egg or egg yolk may work even better than water to increase your cookie's moisture. And occasionally, you may find the recipe was flawed and doomed for failure from the beginning. Whatever you discover, have fun!