Melt chocolate and let it cool to room temperature
Beat butter and icing sugar then add in yolk one at a time
Once all yolks is added in, pour in melted chocolate and beat for 20 minutes
In another bowl, beat egg whites until stiff then fold in flour a little at a time, folding it lightly
Mix the yolk mixture and white mixture, folding lightly
Pour batter into 2 9 inch round pan and bake at 350 F for 30 minutes or until knife inserted in center comes out clean (please do watch out for your oven temperature. each oven has differ temperature and sometimes the accuracy is not reliable unless you have oven temperature measurement)
Cool on rack