Cream the butter in a bowl with a spatula.

Whisk the eggs with the sugar until the mixture turns white. Add the cornflour and cocoa powder. Bring the milk to the boil and pour into the mixture, stirring constantly. Thicken over medium heat, stirring constantly. Leave to cool.

Whisk in the softened butter to aerate the mixture.  

Place an almond and hazelnut cake on a small serving plate. Garnish the entire top generously with cream, using a piping bag with a fluted tip.

Carefully place the second cake on top.

Melt the dark chocolate in pieces in a bain-marie. Remove from the heat and add the cream and butter. Mix well.  

Cover the top of the cake with this icing. Let it run down the sides.

Decorate with hazelnuts, meringue, poached cream... Keep in the fridge !