Before starting this Tiramisu Christmas Log recipe, make sure you have organised all the necessary ingredients for the mascarpone cream.
Separate the eggs and place the yolks in the stand mixer recipient.
Cook the sugar and water until the temperature reaches 121°C. I recommend using a digital thermometer for this operation. Pour the cooked sugar on the egg yolks, beating on low speed. Increase the mixing speed. Beat until the preparation is a pale colour and has doubled in volume.
Strain the gelatine, squeezing it in your hands...
... and add to the warm preparation.
Beat until cooled down completely.
Using a whisk, combine the mascarpone and crème fraîche until homogeneous...
... and gently add to the first preparation.
Add the whipped cream, in which you add the seeds of half a vanilla pod beforehand. Do not beat excessively so the preparation does not collapse. Use a rubber spatula for this step.
Scoop the mascarpone cream into a piping bag. Set aside.
To shape this cake, I used a plastic yule log mould (with the pattern of your choice) that I cut in half with scissors. You can them assemble one half inside the other. This way, starting with a mould that is 50cm long, you can create a length of 25 or 30cm.
Fill the mould halfway up with mascarpone cream.
Even the surface with a spatula or by gently tapping the sides of the mould, to get rid of air bubbles in the cream.
Cut the génoise sponge cake into strips, to the same dimensions as the mould. You will need two identical strips. Place one strip on top of the mascarpone cream.
Using a brush, steep the biscuit with the coffee syrup, made beforehand by combining the cane sugar syrup, instant coffee and alcohol of your choice.
Make sure the whole biscuit is generously steeped in coffee.
Pipe the remaining mascarpone cream on top of the génoise strip.
Even the surface...
... and place the second strip of sponge cake.
Steep with coffee syrup.
Tightly wrap the mould with cling film.
Flip upside down onto a yule log cake board, placed on a baking sheet to make sure the base is perfectly flat.
Place in the freezer for a few hours. Up to this stage, this cake can be prepared the day before, or even several days ahead.
On the day: Gently remove the cling film and plastic mould. Since the log is frozen, the mould should come off easily. Let defrost slowly in the fridge.