Brownies are a tricky business: Homemade recipes have better flavor, while boxed mixes claim best texture. We were tired of having to choose.
Our goal was clear: a homemade brownie with chewiness (and a shiny, crisp, crackly top) to rival the box-mix standard-but flush with a rich, deep, all-natural chocolate flavor.
After testing numerous “chewy” brownie recipes, it became clear that to create a brownie with a truly chewy texture, we had to start from scratch. We consulted our science editor to see if he knew of any tricks that boxed brownies use to achieve their chewiness, and he responded with a phrase that would influence the direction of our research: high-tech shortening system.
First, a chemistry lesson: Fat can be divided into two broad types-saturated (solid) and unsaturated (liquid). The right combination of these fats is what gives box brownies their unique texture. Box brownie mixes already come with the saturated fat component, so when a cook adds unsaturated vegetable oil, the liquid fat and powdered solid fat combine in a ratio designed to deliver maximum chew. To get the same chew at home, we would have to discover the perfect proportion of liquid to solid fat.
We devised a series of recipes that all had roughly the same amount of total fat, but with varying ratios. After much trial and error, we homed in on the ratio that produced the chewiest brownie, and sure enough, the box-mix virtually mirrored our results. To combat greasiness, we replaced some of the oil with egg yolks, whose emulsifiers prevent fat from separating and leaking out during baking.
Now we could focus on the chocolate flavor. Because unsweetened chocolate contains a similar ratio of saturated and unsaturated fat to butter, we could replace some of the butter with unsweetened chocolate, thereby providing more chocolate flavor. Espresso powder improved the chocolate taste as well.
One last thought occurred to us: Only chocolate that is melted and incorporated into the batter actually affects the ratio of fats in the mix. Theoretically, we should be able to incorporate chocolate chunks into the mixed batter, and they should have no effect on texture as long as they didn’t melt until the batter started baking. Sure enough, folding in bittersweet chocolate chunks just before baking gave our chewy, fudgy brownies gooey pockets of melted chocolate and rounded out their complex chocolate flavor.