Recipe: Butter-free Christmas Log

Prepare the pastry cream the day before:
Bring the milk and vanilla sugar to a boil, beat the sugar and egg yolks and whole egg together. Add the flour and mix again. Pour the boiling milk into the mixture, return everything to the pan and thicken over low heat.
The same day:
1/ Make the rolled cake: separate the whites from the yolks. Reserve 2 whites from the pastry cream. Whip the 7 whites until stiff peaks form. Mix the egg yolks and sugar until the mixture becomes pale.
2/ Add the flour and bitter cocoa.
3/ Fold in the stiffly beaten whites
Cover the baking sheet with buttered parchment paper. Pour the batter in the center of the sheet and spread it into a rectangle 1 cm thick. Preheat the oven to 340°F (170°C) (thermostat 6) for 10 minutes.
4/ Remove the sheet from the oven, flip the sponge cake onto a damp kitchen towel and remove the parchment paper.
5/ Roll the cake immediately with the towel. Let it cool this way.
6/ Finish the cake: unroll the sponge, remove the towel. Using a brush, soak the surface of the cake with the syrup (mixture of sugar, water and kirsch). Spread the pastry cream, then roll it up.
7/ Make the ganache: melt the chocolate with the cream and sugar until you get a homogeneous mixture (stir well so it doesn't stick).
To finish... Cover the log with the cold chocolate ganache and streak the ganache with a fork to give it a "wood" appearance, decorate, and enjoy. The log can be made in advance and even frozen.