First prepare the dough for the plumcake.
Whisk the eggs with sugar, salt and vanilla until they are light and fluffy.
Combine oil and milk, then mix in sifted flour and baking powder.
Work until a homogeneous mixture is obtained.

Pour the mixture into the mold lined with parchment paper and cook for about 40 minutes at 180 ° C in a preheated ventilated oven.
Remove from the oven and leave to cool completely.

In the meantime prepare the cream, simply mixing mascarpone and nutella.

Once it is completely cold, cut the cap of the plumcake, which will serve as a lid, and set it aside.
Using a knife or a spoon, dig the base of the plumcake to obtain a sort of "shell", leaving the edges rather thick both laterally and below.
If the cap is very high, you can dig that too.
Stuff the half plumcake shell with the cream.
Arrange the whole Kinder Bueno in the center (keeping those that do not enter for decoration), then finish filling and cover with the shell.

Melt the two types of chocolate in a bain-marie or in the microwave. (Actually it would be better to melt only the milk one, waiting for the next step to dissolve even the dark one.)

Pour the milk chocolate over the plumcake, trying to cover it all evenly.
Let the chocolate solidify in the fridge for at least 30-40 minutes.
Then pour the dark chocolate into a cone (if you had melted it before, like me, you will probably have to melt it again) and decorate the plumcake with thin strands of chocolate, to recall the decorum of Kinder Bueno.
Then also add the pieces of Kinder Bueno Advanced and leave in the fridge again for about 20-30 minutes.

The Bueno plumcake is ready, you just need to bring it to the table and serve it!