Make the cake layer and bake for 15 minutes. Remove from the oven and cover with a kitchen towel.
Mix all the mascarpone filling ingredients until smooth and creamy.
Unroll the cake layer and spread the mascarpone filling, then roll up the cake. Refrigerate for 30 minutes.
Make The Chocolate Ganache.
Mix on high speed until lightened in color and thick enough to spread.
Cover the buche the noel with chocolate ganache using a spatula. Refrigerate for at least 1 hour before serving.