For the cake:
Preheat oven to 200 degrees.
Beat 3 egg yolks. (Save whites)
Edit your remaining whites until stiff.
In a bowl, pour your flour, sugar and vanilla sugar. Incorporate your beaten eggs and mix to a smooth paste and smooth.
Carefully add your egg whites and mix again.
Get out your dough from oven and peel off the treasure. Moisten lightly with a brush of Grand Marnier.
Roll the log on the circle itself and a damp cloth. Let stand for 10 minutes.
For the ganache:
In another pan, pour 5 ounces of water and let it boil. Add to 180 g of sugar.
Now you can train your buche by covering it with your chocolate ganache.
To give it a timber, you can use a fork to make streaks on the length.