Line a 18-20 cm cake pan (7-8 inch) with a circle of baking paper.
Divide the eggs placing the whites in one large bowl and the yolks into another.
Beat the yolks together with the sugar until the mixture becomes thick and creamy. Add yogurt, vanilla and olive oil and beat few more minutes, until combined. Gradually add the flour, mixing gently with a rubber spatula.
In another bowl beat the egg whites until soft peaks form. With the rubber spatula gently fold the whites into the yolk mixture.
Transfer the batter into the prepared pan and bake for about 40 minutes or until a wooden skewer inserted in the centre comes out clean.
Remove from the pan and let cool until room temperature before assembling the cake.
Using a rubber spatula fold the melted chocolate into the ricotta. Mix gently until smooth.
Melt the chocolate in a bowl over a pan of simmering water (double boiler). Transfer it into a large mixing bowl and add the water. Place the bowl in a pan full of ice and start whisking energetically with a hand whisk. Continue for about 5 minutes or until the chocolate mousse starts to thicken. Be careful not to overbeat as the structure of the mousse will become grainy (if this happens, melt it again and repeat the whisking).
To assemble the cake:
Using a serrated knife cut horizontally the base into three layers. Place one layer on a serving plate and evenly spread half of the ricotta frosting on top. Spoon a bit of the chocolate mousse on top (you can do it while it is still liquid for dripping effect). Continue the same process until finishing all cake layers and ricotta frosting. You should still have a good quantity of the chocolate mousse to cover the cake on top and on the sides (unless you want to leave it naked or semi-naked as I did - in this case you can put more between the layers).
Decorate as desired: I used cookies, chocolate and dried apricots.