Spray a jelly roll pan with oil, line with parchment and spray again.
Whip the egg whites until soft peak and set aside.
Melt the chocolate over a double boiler.
whip the yolks and sugar together until very light and fluffy.
Fold the chocolate into the yolk mix, and then fold that into the whites.
Spread the pan and bake at 325 for about 20 minutes until it raises and sets but does not overcook ot it will not roll well.
Take another piece of parchment and place on counter and dust cocoa powder.
Turn the pan out on to this as soon as it comes out of the oven. Let cool completely with a damp towel to keep it from drying out.
Whip the cream, sugar and vanilla until stiff and spread over the cooled sheet.
Taking the back edge of the paper on both sides pull it almost straight back to you at wait level and the cake will roll up just like a jelly roll.
Cut about a quarter of one end off on a bias and set aside. Transfer the remaining cake onto a serving platter and set the small piece on top on the angle side so that it resembles a log.
Decorate with some reserved cream and a dusting of 10x sugar and grated white and dark chocolate.