Melt the chocolate and butter at approx. 120°F (50°C).
Beat the egg whites, adding in the sugar as soon as you start doing so to make sure you obtain a totally smooth mixture.
Add a small amount of beaten egg white to the chocolate and butter mixture, followed by the egg yolks. Use a whisk to smooth out your mixture.
Finish off by adding the remaining egg whites.
BAKING: On a baking mat at 360°F (180°C). 600g to 1000g for a 40 x 60cm mold.