Brownies

Method

1. cook6 min
   bowl over barely simmering water, or 20-second microwave bursts
   dark chocolate + butter, stirred until glossy and fully liquid, then pull it off the heat and let it drop to just-warm — if it is hot when the eggs arrive it curdles them and the batter turns grainy
2. whisk5 min
   vigorous, by hand or on medium-high
   eggs + sugar + brown sugar + salt, until pale, thick and ribboning off the whisk. This is the whole secret of the crackled paper-thin top: the sugar has to dissolve into the egg and trap air, which bakes into a meringue skin. Skip it and the brownie is dull brown on top
3. fold2 min
   chocolate at body temperature
   egg-sugar foam + melted chocolate mixture + vanilla, folded just until uniform and dark, keeping as much of the aeration as you can
4. fold2 min
   stop at the last streak
   + flour + cocoa powder, folded ten or twelve strokes only. Flour in a wet chocolate batter still builds gluten, and an over-stirred brownie bakes tough and cakey rather than fudgy. Fold in walnuts or chips now if using
5. bake25 min
   350°F / 175°C, parchment-lined 8x4 loaf pan or small 6-inch square
   batter spread to about 2 cm deep, until the top is set and cracked but a toothpick in the center comes out with wet crumbs clinging. A clean toothpick means you have made chocolate cake; the fudgy center is residual underbake, and it firms as it cools
6. rest50 min
   in the pan, on a rack, room temperature
   cool completely before cutting — warm brownie is molten butter and unset starch, so the knife smears it into paste. For the cleanest edges, chill 20 minutes and cut with a hot dry blade, wiping between cuts