Recipes engineered for perfection—what exactly does that mean? We take you inside Cook’s Illustrated’s science experiments.
A glossy, crackly top is one of the hallmarks of a great brownie, but achieving it can be elusive. Could the type of sweetener we used be making the difference?
We baked three batches of brownies, one sweetened with granulated sugar, another with brown sugar, and a third with brown sugar and corn syrup.
Only the brownies made with granulated sugar took on an attractive crackly sheen. The other batches had a dull, matte finish. Why does granulated sugar work best? It’s all due to what might be deemed “special effects.” Whether on its own or in combination with corn syrup, brown sugar forms crystals on the surface of the cooling brownie. Crystals reflect light in a diffuse way, creating a matte effect. The pure sucrose in granulated sugar, on the other hand, forms a smooth glasslike surface as it cools that reflects light in a focused way, for a shiny effect.
As for the crackly crust, its formation depends on sugar molecules rising to the surface of the batter and drying out during baking. Since both brown sugar and corn contain more moisture than granulated sugar, the surface of brownies made with either of these sweeteners never dries out enough for a crisp crust to form.
MAKE IT NOW: Our recipe for Chewy Brownies is free through June 2, 2013.