Preparation

1. Butter a round cake pan, dust with flour, and tap out any excess flour.
2. Put a circle of parchment paper cut to fit the bottom of the pan in it.
3. Mix the flour and cocoa powder, then sift two or three times.
4. Separate the eggs; put the whites in a large, completely clean bowl, and put it in the refrigerator.
5. Let the yolks come to room temperature in a large bowl.
6. Mix the butter into the milk, then place the bowl in a warm water bath at 50°C (120°F). (You can also just warm them in the microwave.)
7. Preheat the oven to 180°C (350°F).

Directions

1. Beat together egg yolks and sugar.
   Add the sugar to the egg yolks and beat with an electric mixer until it becomes a thick, whitish foam.
2. Make the meringue.
   
   1. Using a clean electric mixer set to low, beat the whites until they become a half-transparent foam. Add a pinch of salt to help them stiffen, and continue beating.
   2. When the foam has turned white and increased in volume somewhat begin adding the sugar, a third or fourth at a time; add more sugar once the previous portion has mixed completely.
   3. Once all the sugar has been mixed in, increase speed to high until the meringue is stiff enough that the mixer leaves a trail behind it.
   4. Decrease speed to low and continue beating for 3-4 minutes, until it looks shiny and fine-textured, and forms slightly soft peaks and is stiff enough that it will stay in place in the bowl even if you tilt it. If it falls off the beaters or the peaks fall over, it’s not stiff enough. Be careful, though; if you overwhip it will separate, and if the meringue is too stiff, however, the butter won’t mix in properly.
3. Add one third of meringue to egg yolks.
   Add one third of the meringue into the egg yolk mixture, then mix together well with a whisk.
4. Sift half flour into yolk mixture.
   Sift one half of the flour mixture into the egg yolk bowl; fold together with a spatula while rotating the bowl, until just mixed.
5. Add half remaining meringue and remaining flour.
   Gently fold half the remaining meringue mixture into the batter; when mixed, sift in the remaining flour and continue folding until mixed.
6. Add remaining meringue and milk mixture.
   Get a heaping spatula-full of batter and scrape it into the milk-butter mixture; mix well. Add the mixture into the batter and fold gently until mixed. This method makes it easier to mix them together, and makes use of any stiff batter that has stuck to the spatula from the previous step.
7. Pour batter into pan.
   Pour batter carefully into the center of the prepared pan. The batter that is stuck to the bowl won’t rise as readily, so add the scraped batter around the outside edge of the pan where it will cook faster. Smooth the surface with the spatula, then give the pan two or three sharp rotations to flatten it more. Finally, drop the pan gently once or twice on a flat surface to break up any large bubbles.
8. Bake.
   Bake at 180°C (350°F) for 25-30 minutes. To check if it’s done, press the center gently with three fingers; it should feel spongy and make a bit of a crackling sound, and a slight depression should remain. If it only feels soft, it’s not done yet.
9. Drop the pan on a flat surface, then cool.
   Immediately after removing from the oven, hold the cake pan right side up about 20cm (8") above a table, and drop it so it lands flat; this will prevent the cake from falling. Put the pan upside-down on top of a paper towel on a wooden cutting board to cool slightly, about 5 minutes. Remove the cake from the pan, but leave the parchment paper on. Let cool completely, right side up, on a cake rack. Once it is completely cooled, cover the cake (or wrap it in a plastic bag) to keep it from drying; remove the parchment paper when you’re ready to use it.