Chocolate Sponge
Beat the egg whites with the sugar. Add the egg yolks to the chocolate and butter, which you have melted at approx. 120-130°F (50-55°C). Incorporate a small amount of beaten egg white to make the mixture more liquid, followed by the remaining egg whites and finally the sifted flour. Spread on a tray and bake at 170ºC around 35 minutes. Reserve to the refrigerator.