Bring the cream to a boil and pour over the melted chocolate. Mix well and let sit at room temperature until is reaches thick spreadable consistency. You can prepare this a day in advance.

Preheat the oven to 350 degrees. Prepare a 18 x 12" baking sheet, by lining with parchment paper. butter the paper and spinkle a little flour to help you remove the sponge once baked.

Whisk the egg yolks with 1 1/2 cups of sugar until the mixture reaches a pale yellow color in a large mxing bowl.

In a small mixing bowl, sift together the cocoa powder and potato starch.

Whip the egg whites until stiff.

Fold half the egg whites into the yolk mixture, then fold in the cocoa mixture, and finally the rest of the egg whites.

Spread the sponge mixture into the prepared pan and bake for 15 minutes or until the middle is firm to the touch

Cut a piece of parchment paper larger than the pan, placing on your counter and sprinkle with the remaining sugar. Invert the cake on the parchment and carefully peel off the parchment paper. With a sharp knife make a score mark 1 inch along one of the long edges. Allow the cake to cool.

Boil the cream and add to the melted chocolate. Mix and then allow to cool to a spreading consistency.

Spread the filling on the cake with an offset spatula or knife. Reserve a tablespoon or two.

Roll up the log (from the longer edge) using the paper. Don't worry if you have cracks; in fact is it better with cracks as it will look like a natural piece of wood. Place the roll on more parchment paper placed on your serving platter.

With a sharp knife, make a diagonal slice off the cake. This is your side branch. Place the diagonal edge against the log, affixing with the remainder of the filling.

Allow the frosting to set for a few hours. Slice and serve with whipping cream and sit back and enjoy the compliments.