In a bowl pour the biscuit crumbles, cacao powder and the melted butter. Mix well.
Cover the bottom of a baking form with removable edges with the crumble mixture. Press it with your hand to get it eventually.
Place the bottom in the fridge while preparing the rest.
Place the gelatin in cold water for 10 minutes.
In a casserole pour the nutella and the chocolate. Heat it up and make sure the chocolate gets melted.
Heat up 100 ml of whip cream, and when it starts boiling take it away from the heat.
Squeeze the gelatin and melt it in the whip cream while stirring.
Add the warm whip cream to the chocolate and mix well.
Let it cool down for a few minutes.
Whip the rest of the whip cream to a hard mousse.
Mix gently together the chocolate mixture with the whip cream.
Pour it over the cake bottom.
Place the cake in the fridge for minimum 3 hours.
Before serving the cake decorate it with raspberries and whipped cream.