We consulted one of our favorite cookbooks, BakeWise, and found that this crispy top crust is actually a layer of meringue. That's right - whipped egg whites and sugar! It happens in recipes where the the butter and sugar are creamed together and then the eggs are added. The more the mixture is beaten once the eggs are added, the more prominent this crust.
If you're like us and you love the crispy top, just beat the batter as much as possible after adding the eggs and before adding any other ingredients. We tried this by hand using a whisk in with our recent batch of Hershey's Ultimate Chocolate Brownies and got a decent, though fairly thick crust. We expect that we'd get an even more impressive crust if we used a standing or hand mixer instead.
This recipe from Martha Stewart has you beat the eggs and sugar for a full 10 minutes!
• Chocolate Brownies from Martha Stewart
Conversely, if you're not a fan of crusts, just mix the batter as little as possible once you add the eggs. You might even whisk the eggs before adding them to the batter so they'll blend in more quickly and smoothly.
This method also works for cookies and cakes. Now that we know the secret, we're excited to experiment with all our baking!
What do you think: crispy crust, yay or nay?
Related: Five Ways to Eat Dark Chocolate
(Image: Martha Stewart)