How do I get the crackly, shiny top?
That crinkly, shiny top is helped along by a few things working together: well-whipped eggs, plenty of sugar, and giving the sugar time to dissolve so it can form that thin, meringue-like crust as the cookies bake. Beat the eggs, sugars, and vanilla for a full 2 to 3 minutes until the mixture looks thicker, glossier, and starts to ribbon off the whisk. (A hand mixer makes the ribbon stage much easier.) Then whisk in the warm (not hot) melted butter and cocoa so the cocoa hydrates smoothly and the batter turns shiny.
Do I need to chill the batter?
No. These are designed to bake right away. If your kitchen is very warm and the batter feels loose, let it sit for 5 to 10 minutes to thicken slightly, or pop the bowl in the fridge while the oven finishes preheating.
Why did my cookies turn cakey?
Most common reasons are too much flour, overbaking, or not whipping the eggs and sugar enough. Spoon and level your flour, and pull the cookies when the edges look set but the centers still look a little soft.
Can I use Dutch-process cocoa?
Yes. Dutch-process cocoa gives a darker color and smoother chocolate flavor. Natural cocoa works too. Use whichever you have.
Can I make them gluten-free?
You can swap the all-purpose flour for a 1:1 gluten-free baking blend that includes xanthan gum. The texture will be slightly more delicate but still fudgy.
