Line the cake pan with paper. Preheat the oven to 375ºF/190ºC.
Make the spongecake base. Break the eggs into a bowl, beat and mix in the granulated sugar. When it's mixed together, beat with a hand mixer over a double broiler to heat the mixture up to body temperature.
When the batter is at body temperature, take the bowl off the double broiler and beat. Once it has reached the consistency shown in the photo, turn the speed of the hand mixer down to low, and turn it around the bowl slowly to make the texture of the batter smooth.
Add milk and mix in.
Sift in the cake flour, and fold in.
Mix it until the batter reaches this consistency. It will be nice and shiny.
Pour the batter into the lined cake pan, even out the surface and bake at 375ºF/190ºC for about 13 minutes.
When the sponge cake base is baked, peel off the paper, and cover with the same paper to prevent drying out as it cools.
Add granulated sugar and chocolate syrup to the heavy cream, and beat with the bowl suspended over a bowl filled with ice water until the cream forms soft yet firm peaks.
About 2 cm of the edge of the sponge cake base will be used as the center, so score it lightly with a knife. Put the paper you used to bake the cake underneath it so it's easier to roll up.
Spread half the whipped cream on the cake, and roll it up. To roll the cake, first press down on the core part tightly.
Then when a center is formed, roll the cake up while pulling on the paper.
Finally use a ruler or something to neaten the roll. Wrap the rolled cake in the paper and chill in the refrigerator for a while until it settles.
Cut both ends diagonally to make the side branches. Attach with toothpicks.
Spread the rest of the whipped cream on the cake, and make the tree bark pattern with a spoon or fork. Draw the tree rings with the chocolate pen, decorate with Christmas like items and it's done.