In a bowl, place the cream cheese, powdered sugar, and vanillin and mix all together.
Add the Dairy cream 35% fat, mix, and then beat the mixture with a hand mixer until it becomes a smooth cream. Cover with plastic wrap and refrigerate.
In a bowl, add the flour and powdered sugar and mix.
In another bowl, add the cocoa powder, and hot water, mix, and cover with plastic wrap. In a mixer, beat the egg yolks along with the 15g of sugar with the whisk attachment until the mixture becomes fluffy. Transfer the mixture to a large bowl. In the mixer bowl, beat the egg whites until they become a meringue. Add the 70g sugar in 3 batches while continuing to mix. Pour 1/3 of the meringue into the bowl with the yolk mixture and fold gently with a whisk.
Sift in the flour mixture and mix. Pour in the cocoa mixture and mix lightly with a spatula, adding the remaining meringue in batches.
Pour the mixture into a baking pan lined with parchment paper and spread it evenly. Bake in a preheated fan oven at 160 degrees (Celsius) for about 13 minutes.
Allow the sponge cake to cool with a towel over it.
Trim the edges of the sponge cake to form an even rectangle.
Fluff up the cream and use a piping bag to spread it over the sponge cake.
Wrap the sponge cake carefully to prevent it from breaking and refrigerate for 2 hours.
In a bowl, add the finely chopped couverture and the hot OLYMPOS cream with 35% fat and mix.
Allow to cool in the refrigerator for 10-15 minutes.
In a bowl, add the cream cheese, and the ganache, and beat with a hand mixer until the mixture becomes fluffy.
Pour the cream mixture into a piping bag with a round tip attached and spread it over the log.
Use a pastry brush to make lines on the log (by brushing it).
Optionally garnish with a little bit of grated couverture.