These cookies were popular, but I always thought there was room for improvement.

Rolled in powdered sugar before going into the oven, chocolate crinkle cookies (aka earthquakes) feature dark chocolaty fissures that break through the bright white surface during baking. They have a striking appearance, with an irresistible chocolaty richness to back it up.

Or at least that’s how I think they should be. Before my days as a test cook, I worked at a bakery where I made batch after batch of chocolate crinkle cookies. These cookies were popular, but I always thought there was room for improvement. They were a little too sweet, the chocolate flavor was underwhelming, and the cracks were sparse and more like gaping chasms than fissures. And because the confectioners’ sugar coating all but vanished in the oven, those few cracks weren’t even that noticeable. I wanted a cookie with deep chocolate flavor and only enough sweetness to balance the chocolate’s bitterness, a moist and tender— but not gooey—interior, and plenty of small irregular crinkly fissures breaking through a bright-white surface.

Dough Details

I started by trying a handful of published recipes, limiting myself to those that called for preparing the dough by hand—no stand mixer required—since the melted chocolate and melted butter should make this a loose, easy-to-stir dough. To my surprise, no matter what type of chocolate a recipe called for (and these were all over the map, from unsweetened, bittersweet, and semisweet bar chocolate to cocoa powder) or how much sugar was used, the results were all strikingly similar to the bakery cookies: They were too sweet, with muted chocolate flavor. Furthermore, they all had cracks that were too wide yet few in number.

The most promising recipe of the bunch achieved decent chocolate flavor from 3 ounces of unsweetened chocolate, 3 ounces of bittersweet bar chocolate, and 1⁄4 cup of cocoa powder. Since these cookies were too sweet, my first decision was to drop the bittersweet chocolate because it contains added sugar. In its place, I upped the unsweetened chocolate to 4 ounces and the cocoa powder to 1⁄2 cup. I decided to see how these changes fared and left the sugar alone, at 13⁄4 cups. I didn’t go into sugar shock at this first attempt, but the cookies were still a bit cloying and not chocolaty enough. Dropping the sugar down to 11⁄2 cups helped bring the chocolate flavor to the fore and put the sweetness in an acceptable range.

My cookies were impressively chocolaty now, but I felt that they could taste even better. Taking a cue from one of the recipes I’d tested, I substituted brown sugar for the granulated, since it would lend a more complex sweetness, with a molasses undertone that would complement the chocolate. After I added some espresso powder, which helps heighten chocolate flavor, my cookies really hit the mark for bold chocolate taste. It was time to move on to issues of appearance.

Cracking the Code

Just as I’d seen in the initial recipe tests, the cracks on my cookies were too few and too wide, and the cookies weren’t spreading enough—they looked a bit humped. In the past, we’ve found that leaveners not only contribute to rise and spread in cookies but also help create a more crackly, fissured surface. Before a cookie sets in the oven, bubbles produced by the leavener rise to the surface and burst, leaving fissures. In our Gingersnaps recipe we found that baking soda alone was most effective, while our Chewy Sugar Cookies benefited from both baking powder and baking soda. I’d started my testing with baking powder since it was the most commonly used leavener in the recipes I’d seen, but baking soda, which requires an acidic ingredient to work, was also an option since my recipe included brown sugar and espresso powder.

Cookies with baking soda alone weren’t impressive. Using 1⁄4 teaspoon didn’t provide enough leavening power, and 1⁄2 teaspoon gave the cookies a metallic aftertaste. Baking powder, as I already knew, did a decent job by itself, but a combination of baking powder and baking soda proved to be the winner. These cookies spread nicely, without any hump, and they had a more crackly surface than anything I’d produced thus far. However, the cracks still gaped and were fewer in number than I had hoped for.

I wondered if the temperature of the dough was playing a role. Because it was too fluid to work with right after I mixed it, I had been refrigerating the dough overnight before portioning the cookies and baking them. This is a common crinkle cookie step, but maybe it was doing more harm than good. To find out, I baked two more batches—one after refrigerating the dough for 4 hours and another after letting the dough sit at room temperature until the melted chocolate and butter cooled just enough to make the dough workable, which took only 10 minutes—and compared these with my current recipe that had the refrigerated overnight rest. My hunch was right. The cookies made after the 10-minute rest were the best of the group, with finer and more numerous cracks than the other two batches (and it didn’t hurt that I didn’t have to wait as long to enjoy them either).

What was happening? The cookies made with refrigerated dough were cold in the center and thus hadn’t spread much by the time the heat of the oven had dried out their exteriors. This meant that these cookies did almost all their spreading after that dried exterior had formed, forcing the cracks to open wide as the cookies spread. Meanwhile, the room- temperature dough had already spread somewhat by the time the exterior dried in the oven. Minimal spreading once the exterior had dried meant smaller, more numerous cracks. Though I wondered if the cracks could be even more fine and numerous, they were looking pretty good—certainly the best yet— so I decided to turn my attention to the signature sugar coating.

Sugar Coated

As with the cookies I’d made at the bakery, the coating of confectioners’ sugar on these cookies was faded. I recalled that some of the recipes in my early tests, flawed as they were, produced cookies with a picture-perfect bright-white exterior. I realized that they all called for rolling the cookies in granulated sugar before the powdered sugar. When I added this step to my recipe, not only did the powdered sugar stay put, but the cracking improved significantly. These cookies had my ideal fine cracks all over the surface.

As for the increase in fine cracks, our science editor explained that the crystalline structure of granulated sugar was key.

How could a tweak as simple as this lead to such big changes? A likely explanation for the improved bright-white appearance was that the heavy coating of granulated sugar created a barrier that kept the fine-grained confectioners’ sugar from dissolving and disappearing into the dough. As for the increase in fine cracks, our science editor explained that the crystalline structure of granulated sugar was key. Because sugar (in any form) is hygroscopic, a layer on the outside of the cookie will pull moisture from the inside, drying out the cookie surface so it is more prone to cracking. And granulated sugar is more effective than powdered sugar. The crystals in granulated sugar dissolve as they draw out moisture but then rapidly recrystallize as that moisture burns off in the heat of the oven. And once recrystallized, the sugar continues to pull more water from the cookie, creating a very dry top surface that breaks into numerous fine cracks as the cookie spreads.

Finally I had the cookie I’d always pictured. Combined with their deep chocolate flavor, these chocolate crinkle cookies were all they were cracked up to be.