Beat the eggs with the sugar, add the oil and yoghurt, then the dry ingredients and stir until you get a smooth cake batter. Divide into 3 parts and bake in a round form, with baking paper on the bottom. Put the milk to come to a boil, add the egg yolks carefully and stir.
Add the sugar and flour gradually, stirring constantly to thicken. Stick the layers together, thoroughly coating them with cream and then leave them to cool. Beat the cream and smear on the cake.
For the biscotti: beat the eggs with the powdered sugar and add the flour, while stirring. Using a spoon, in a tray with baking paper, shape the biscotti (pour in the dough and spread it out). Bake them carefully without letting them turn black.
Cut the ready circles in halves and stick them to the sides of the layers to form a cake. To complete it, pour on melted chocolate in a water bath.