For the molehill cake, coarsely chop 100 g of the chocolate and finely chop with the nuts in a chopper. Preheat the oven to 175 °C.
Grease a cake tin well and sprinkle with breadcrumbs. Cream the butter in a bowl with the cane sugar until the sugar has dissolved.
Separate the eggs and gradually stir the egg yolks into the butter mixture. Mix in the chocolate-nut mixture with the baking powder.
Beat the egg whites with 1 pinch of salt and 1 packet of vanilla sugar until stiff peaks form and slowly fold into the batter.
Pour the batter into the pan and bake in the oven (center, convection oven 170 °C) for about 1 hour, until no batter sticks to a wooden stick inserted in the pan.
Let the cake rest briefly in the pan, then turn the cake out onto a cake rack and let it cool completely.
Just before serving, cut off a lid about 3 cm thick from the top of the cake and crumble it. Peel the bananas and cut into cubes.
Mix them with lemon juice to prevent them from turning brown. Finely grate the remaining 50 g of chocolate. Whip the cold cream with cream stiffener, sugar and 1 packet of vanilla sugar until very stiff.
Mix in the chocolate shavings. Mix ⅓ of the whipped cream with the marinated banana cubes and fill the cake with it.
Pile the remaining chocolate fudge in a dome shape on top of the cake so it looks like a molehill. Sprinkle the dark cake crumbs evenly over the top and make the molehills