There are two things to remember if you want brownies with a shiny, crackly crust: 1. Follow a recipe (like this one!) that incorporates melted chocolate into the brownie batter. Using only cocoa powder can create a dull matte finish.2. Beat sugar into the melted chocolate while it's hot, and then beating the eggs into the batter incorporates air, which will rise to the surface during baking and create a thin, meringue-like layer.