Mince the chocolate bar and melt together with the butter by immersing in 70-80°C hot water bath (if this is too much trouble, you could microwave it).
Use a whisk to beat 3 egg yolks for 2 minutes (it should start to become white). Once beaten and slightly warm, add to the mixture in Step 1 and mix.
Whisk 3 egg whites. Once stiffened, add the sugar in 2 to 3 portions and mix. Continue mixing until the meringue forms peaks.
Add a third of the meringue to the chocolate bowl from Step 2 and mix. Lightly combine the rest of the meringue. Try to leave the delicate bubbles as intact as possible.
Lightly mix in the sifted dry ingredients. Pour into a baking-sheet lined pan and bake in the oven at 160°C for 45 minutes.
This is what it looks like after baking. Once it's cooled, remove it from the pan and refrigerate. After half a day, it'll deflate.
Bonus: For the baking sheet, cut into a large circle and insert cuts into the high parts. Apply margarine to secure the paper on the pan.
Story Behind this Recipe
Cocoa powder is expensive! I wanted to make things that are a bit easier on the wallet.
It's best to bake this in the morning and eating it after dinner. You'll want to eat it right away, but be patient and let it sit for 10 hours. If you have heavy cream, add to Step 1 for an even richer flavor.