Place flour, baking powder, sugar and vanilla sugar in a wide container.
Mix everything briefly with your fingers.
Then add sliced butter at room temperature and knead the crumbly dough.
Then add grated orange peel and whole eggs.
Knead a smooth dough.
Wrap it in transparent foil and leave it in the fridge for half an hour to rest.
During this time, make the hazelnut filling.
Put butter, milk, sugar and vanilla sugar in a bowl on the stove.
Heat while stirring until the butter and sugar are melted.
When it boils, add chopped and ground toasted hazelnuts and mix everything well.
Leave aside to cool.
After half an hour, take the dough out of the fridge and roll it out on baking paper to the dimensions of a large oven tray and transfer it with the paper to the tray.
Then spread the dough with rosehip marmalade or another.
Spread the filling on top of the marmalade and spread it evenly.
The cake is baked in an oven heated to 356 degrees for 20 minutes.
Leave the baked cake to cool at room temperature, then cut it into 5 centimeter squares, and then cut each square diagonally to make triangles.
For the glaze, melt dark chocolate with oil in a steamer.
Dip the sharp parts of the triangles into the still hot melted chocolate and leave them on the baking paper to harden.