There are two steps to making brownies with a shiny crackly crust:

  1. Follow a recipe that incorporates melted chocolate into the brownie batter. Brownies that use only cocoa powder often bake up with a dull matte finish.
  2. Once you add the eggs to the batter, beat the mixture for 2-3 minutes. Beating the eggs with the sugar already in the batter will incorporate air, which will rise to the surface during baking and create a thin, meringue-like layer.