In a food processor, roughly chop the couverture. (Should be small but not super fine)Set aside.

In a clean glass bowl, beat the egg whites until stiff peaks form. Set aside

In a separate large bowl, beat the egg yolks and sugar until light and fluffy.

Add the flour and baking powder and mix well.

Add the oil and water and mix well.

Add in the ground chocolate and mix until combined.

Fold in a third of the egg whites to loosen the batter. Then gently fold in a third at a time until combined. Do not over mix

Pour the mixture into a greased cake tin (two thirds full) and bake in a preheated oven at 165C until the cake springs back on touch (depends on cake tin size but between 30/40 minutes.

Allow the cake to cool completely before removing from tin

For the topping:
In a small pot add the cream and two of the bar ones (roughly broken up)

Put the heat on medium and mix continuously until the chocolate has melted. This takes some time because of the nougat.

Finally add the lindt to the pot and stir until combined. Allow to cool slightly before pouring over the cold cake.

Decorate the cake as you like, I always slice up the remaining bar one for on top and then add whatever else looks pretty.