Crêpes and chocolate mousse cake

Make the crêpes: Whisk the eggs, flour, salt, cacao and sugar in a bowl. Add the milk and melted butter, and finish your liquid batter. Heat up a pan under medium heat, brush the bottom with butter and pour one ladle of batter onto the pan. Cook for two minutes on each side. Repeat until you run out of batter. 

Make the mousse: using the microwave or a bain-marie, melt the butter and chocolate together. Separate the egg whites from the yolks, keeping each in two large bowls. Add a pinch of the egg whites and whisk using an electric mixer, until stiff. Set aside.  

In the egg yolks bowl, add the icing sugar and crème fraîche and blend well. Then add the melted chocolate and butter mix.  Pour this mix in the egg whites, incorporating it gently with a spatula. Finish with a pinch of fleur de sel. 

Make the crêpes cake : on a plate, lay one crepe and spread a thin layer of chocolate mousse on top. Add a crêpe on top. Repeat until you run out of chocolate mousse, finish with a crêpe on top. Let it set in the fridge for 1h before serving.