Melt the butter in a saucepan over low heat. Mix water, cocoa and vanilla sugar.
Remove the saucepan from the heat. Separate the eggs and mix in 2 egg yolks.
Pour the mixture into a large baking dish and add the sugar. Combine the flour and baking powder and sift them into the mixture. Mix well.
Beat the egg whites until stiff in a perfectly clean glass or metal bowl. Using a spatula, fold about 1/3 of the egg whites into the rest of the batter. Then add the rest of the egg whites and gently mix them into the batter. Do not mix more than necessary.
Line the bottom of a 24-inch round pan with parchment paper. Pour the batter into the mold and bake the cake next to the bottom of the oven for about 20 minutes, at 180 degrees. Use a cake stick, or knitting needle, in the middle of the cake to check that the cake is completely finished, the stick should come out completely clean when the cake is done.
Cool the cake on a wire rack.
Thaw the raspberries. Then pass them through a sieve to remove all the seeds. It’s tedious work but it’s not good to get hard raspberry pips in the soft cream.
Put the gelatin plates in cold water for a few minutes.
Spread about 1/3 of the raspberry purée in a saucepan. Heat until it begins to smoke. Squeeze the water from the gelatin plates and dissolve them in the hot mash. Mix well. Then add the rest of the raspberry purée.
Whip a soft cream of cream, powdered sugar and vanilla sugar. Incorporate the raspberry puree into the cream using a spatula. Leave the cream to rest for a few minutes in the refrigerator before spreading it on the bottom of the pie.
Roughly chop the chocolate. Boil the cream and pour it over the chocolate. Leave the cream to rest and heat the chocolate for about 2 minutes, before stirring quickly with a spatula until all the chocolate is melted. If all the chocolate does not melt, you can gently put the bowl in a bain-marie, possibly at low temperature in the microwave, until the chocolate melts.
Cool chocolate ganache on kitchen counter until thick enough to drip off. Using a large spoon, empty the chocolate in thick strips at random onto the raspberry cream.
Decorate the cake with a generous layer of fresh fruit and berries, and preferably a few scoops of chocolate, if you have any.