MAKES: 1 x 9x13” pan, or 1 x 8x8” pan (extra thick)
Preheat oven to 175°C. Grease a 9x13” pan or line with parchment paper with overhangs for easy removal.
Put cocoa powder, chopped chocolate, and espresso powder in a heat-proof bowl.
Brown butter: Melt butter in a saucepan over medium-low heat. Once foaming and spitting, stir and scrape bottom with a spatula every 10-15 seconds. Grainy white milk solids will begin to appear on the bottom. Continue for 5-10 minutes (go by senses, not time). When foam clears and spitting noises go silent, watch closely: The milk solids will toast in seconds. As soon as the solids turn brown and smell nutty, remove pan from heat so it doesn’t burn.
Immediately pour hot brown butter into prepared bowl to bloom cocoa and melt chocolate. Stir until smooth. Set aside to cool.
Foam eggs: With a stand or hand mixer, whip sugars, vanilla, and eggs on medium-high until thick, smooth, fluffy, and lightened in color. For very moist, rich brownies, stop after 4-5 minutes. For slightly more height and fluff, whip 8-10 minutes until very thick and pale.
Reduce speed to low. Slowly pour chocolate-butter mixture into egg foam mixture until incorporated.
Using a spatula, fold in flour and salt until just incorporated. Fold in additional chocolate if using. Batter will be very thick.
Scoop and spread batter evenly into prepared pan.
Bake 25 minutes until surface is glossy and just set (not jiggly in center). Do not overbake. They will finish cooking as they cool.
Let cool at least 30 minutes before removing from pan to slice.
NOTES
White sugar + foaming eggs = fudgy centers with classic glossy, crackly tops. The thicker your egg foam, the glossier/cracklier your top crust. Beating for multiple minutes (vs. just whisking together, or only beating until incorporated) dissolves the sugar and aerates the eggs, just like meringue.
Brown butter deepens flavor and evaporates excess water in the butter. If you don’t want to brown the butter, melt it in a saucepan with the chopped chocolate, stirring until smooth. Pour over cocoa powder and espresso powder. Stir until smooth.
For extra thick brownies, use an 8x8” pan. Bake time might be a bit longer.
Cocoa vs. chocolate: Cocoa = moister, fudgier brownies; cocoa powder contains no cocoa butter (solidifies when cool) and adds no moisture to the batter (so you don’t need to add more flour to compensate). Chocolate adds complexity of flavor, but might contain added sugar, emulsifiers, etc. that are not ideal.
https://docs.google.com/document/u/0/d/e/2PACX-1vR9jM9oNQ3DW24UVKybx0CqevEy-hvPUULHlNxqOMnOShAFMAGRIpacdmd45v-k1yMK4t0EvH0T05y2/pub?pli=1#h.koneopo30zzb