For the glacage paradis: Bring the cream to a boil. Pour the cream on top of the dark chocolate. Mix gently. In a saucepan, bring 8 3/4 ounces water and the superfine sugar to a boil. Add the cocoa powder and the double cream, then bring back to a boil. Delicately mix the dark chocolate and the cocoa powder mixtures together. Refrigerate for 24 hours.
For the dacquoise: Preheat the oven to 375 degrees F/190 degrees C. Mix together the ground hazelnut and the confectioners' sugar. In a separate bowl, whisk the egg whites using a hand mixer. When the egg whites have doubled in volume, add in the superfine sugar. Delicately incorporate the hazelnut mixture. Smooth into a circle on a baking tray covered in parchment paper. Sprinkle with confectioners' sugar and bake for 10 minutes. Leave to cool. Then cut the dacquoise the bottom of the cake pan.
For the praline: Preheat the oven to 320 degrees F/ 160 degrees C. Roast the hazelnuts then add them to the granulated sugar, in a blender. Blend until smooth, at least 5 minutes.
For the feuillantine: Fill a pot with an inch or so of water. Bring to a boil and place a non-reactive bowl over the top to create a double-boiler. Melt the white chocolate and 14 1/8 ounces/400 grams of the praline together. Then add the biscuits and mix well.
For the chocolate mousse: Whisk the cream to stiff peaks. Melt 9 1/2 ounces/270 g of glacage to liquid but still cold. Whisk the liquid glacage into the cream. Reserve the remaining glacage in the refrigerator.
To assemble, place the dacquoise disk at the bottom of the cake pan. Fill with the chocolate mousse. Place the feuillantine in a very thin layer on top. Leave in the freezer for a minimum of 5 hours.
Heat the remaining glacage to 104 degrees F/40 degrees C in a double boiler. Two hours before serving, remove the cake pan from the freezer and remove the cake from the pan. Immediately cover the whole cake with the glacage. Enjoy.